feat: Add MCP Elicitation support (#332)
* feat: implement MCP elicitation support for interactive user input Adds comprehensive elicitation functionality according to MCP 2025-06-18 specification: Core Features: - ElicitationAction enum (Accept, Decline, Cancel) - CreateElicitationRequestParam and CreateElicitationResult structures - Protocol version V_2025_06_18 with elicitation methods - Full JSON-RPC integration with method constants Capabilities Integration: - ElicitationCapability with schema validation support - ClientCapabilities builder pattern integration - enable_elicitation() and enable_elicitation_schema_validation() methods Handler Support: - create_elicitation method in ClientHandler and ServerHandler traits - Integration with existing request/response union types - Async/await compatible implementation Service Layer: - Basic create_elicitation method via macro expansion - Four convenience methods for common scenarios: * elicit_confirmation() - yes/no questions * elicit_text_input() - string input with optional requirements * elicit_choice() - selection from multiple options * elicit_structured_input() - complex data via JSON Schema Comprehensive Testing: - 11 test cases covering all functionality aspects - JSON serialization/deserialization validation - MCP specification compliance verification - Error handling and edge cases - Performance benchmarks - Capabilities integration tests All tests pass and code follows project standards. * feat: add typed elicitation API with enhanced error handling - Add new 'elicitation' feature that depends on 'client' and 'schemars' - Implement elicit<T>() method for type-safe elicitation with automatic schema generation - Remove convenience methods (elicit_confirmation, elicit_text_input, elicit_choice) - Add ElicitationError enum with detailed error variants: - Service: underlying service errors - UserDeclined: user cancelled or declined request - ParseError: response parsing failed with context - NoContent: no response content provided - Update documentation with comprehensive examples and error handling - Add comprehensive tests for typed elicitation and error handling * fix: correct elicitation direction to comply with MCP 2025-06-18 - Remove CreateElicitationRequest from ClientRequest - clients cannot initiate elicitation - Move elicit methods from client to server - servers now request user input - Add comprehensive direction tests verifying Server→Client→Server flow - Maintain CreateElicitationResult in ClientResult for proper responses - Update handlers to reflect correct message routing - Add elicitation feature flag for typed schema generation Fixes elicitation direction to match specification where servers request interactive user input from clients, not the reverse. * feat: add elicitation capability checking for server methods - Add supports_elicitation() method to check client capabilities - Add CapabilityNotSupported error variant to ElicitationError - Update elicit_structured_input() to check capabilities before execution - Update elicit<T>() method to check capabilities before execution - Add comprehensive tests for capability checking functionality - Tests verify that servers check client capabilities before sending elicitation requests - Ensures compliance with MCP 2025-06-18 specification requirement * fix: json rpc message schema * fix: doc tests * fix: cargo nightly fmt checks * fix: clippy * refactor: separate elicitation methods into dedicated impl block for RoleServer - Move (supports_elicitation, elicit_structured_input, elicit) to separate impl block - Move ElicitationError definition to elicitation methods section - Keep base methods (create_message, list_roots, notify_*) in main impl block with macro - Add section comments to distinguish general and elicitation-specific methods * revert: rollback LATEST protocol version to V_2025_03_26 * fix: remove protocol version assertions - Remove assertions for V_2025_06_18 protocol version * fix: fmt checks * feat: add timeout support for elicitation methods - Add peer_req_with_timeout macro variants for timeout-enabled methods - Implement create_elicitation_with_timeout() method - Implement elicit_with_timeout() for typed elicitation with timeout - Refactor elicit() to use elicit_with_timeout() internally - Add 8 comprehensive timeout tests covering validation, error handling, and realistic scenarios - Fix elicitation feature dependencies in Cargo.toml - Add proper feature gates for elicitation-specific code * feat: add timeout validation to prevent DoS attacks - Add InvalidTimeout error variant for comprehensive validation - Implement validate_timeout function with security limits (1ms-300s) - Integrate validation into peer_req_with_timeout macros - Add comprehensive security tests for timeout validation - Prevent DoS attacks through unreasonable timeout values * feat: separate UserDeclined and UserCancelled elicitation errors According to MCP specification and PR feedback, decline and cancel actions should be handled differently: - UserDeclined: explicit user rejection (clicked "Decline", "No", etc.) - UserCancelled: dismissal without explicit choice (closed dialog, Escape, etc.) Changes: - Split ElicitationError::UserDeclined into two distinct error types - Update error handling logic to map each ElicitationAction correctly - Improve documentation with proper action semantics - Add comprehensive tests for new error types and action mapping - Update examples to demonstrate proper error handling This provides better error granularity allowing servers to handle explicit declines vs cancellations appropriately as per MCP spec. * feat: add compile-time type safety for elicitation methods Add ElicitationSafe trait and elicit_safe\! macro to ensure elicit<T>() methods are only used with types that generate appropriate JSON object schemas, addressing type safety concerns from PR feedback. Features: - ElicitationSafe marker trait for compile-time constraints - elicit_safe\! macro for opt-in type safety declaration - Updated elicit<T> and elicit_with_timeout<T> to require ElicitationSafe bound - Comprehensive documentation with examples and rationale - Full test coverage for new type safety features This prevents common mistakes like: - elicit::<String>() - primitives not suitable for object schemas - elicit::<Vec<i32>>() - arrays don't match client expectations Breaking change: Existing code must add elicit_safe\!(TypeName) declarations for types used with elicit methods. This is an intentional safety improvement. * Revert "feat: add timeout validation to prevent DoS attacks" This reverts commit 829624212b4fb55ec32566329af7ec195c987ef5. * fix: correct doctest example in elicit_safe macro documentation - Remove invalid async/await usage in doctest example - Comment out the actual usage line to show intent without compilation errors - Maintain clear documentation of the macro's purpose and usage * refactor: remove redundant elicitation direction tests - Remove test_elicitation_not_in_client_request (duplicated functionality) - Remove redundant ServerRequest match in test_elicitation_direction_server_to_client - Direction compliance is already verified by the remaining comprehensive test - Reduces test fragility and maintenance burden * feat: add elicitation example with user name collection - Add elicitation server example demonstrating real MCP usage - Implement greet_user tool with context.peer.elicit::<T>() API - Show type-safe elicitation with elicit_safe! macro - Include reset_name tool and MCP Inspector instructions - Update examples documentation and dependencies * fix: add Default impl to ElicitationServer for clippy Resolves clippy::new_without_default warning by implementing Default trait for ElicitationServer struct.
This commit is contained in:
Andrei G
GitHub
parent
4e6c57ef14
commit
81ff3159f9
12 changed files with 2287 additions and 4 deletions
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@ -79,6 +79,7 @@ default = ["base64", "macros", "server"]
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client = ["dep:tokio-stream"]
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server = ["transport-async-rw", "dep:schemars"]
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macros = ["dep:rmcp-macros", "dep:paste"]
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elicitation = []
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# reqwest http client
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__reqwest = ["dep:reqwest"]
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@ -201,3 +202,8 @@ path = "tests/test_message_schema.rs"
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name = "test_progress_subscriber"
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required-features = ["server", "client", "macros"]
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path = "tests/test_progress_subscriber.rs"
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[[test]]
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name = "test_elicitation"
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required-features = ["elicitation", "client", "server"]
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path = "tests/test_elicitation.rs"
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@ -21,6 +21,10 @@ impl<H: ClientHandler> Service<RoleClient> for H {
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.list_roots(context)
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.await
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.map(ClientResult::ListRootsResult),
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ServerRequest::CreateElicitationRequest(request) => self
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.create_elicitation(request.params, context)
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.await
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.map(ClientResult::CreateElicitationResult),
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}
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}
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@ -86,6 +90,35 @@ pub trait ClientHandler: Sized + Send + Sync + 'static {
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std::future::ready(Ok(ListRootsResult::default()))
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}
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/// Handle an elicitation request from a server asking for user input.
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///
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/// This method is called when a server needs interactive input from the user
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/// during tool execution. Implementations should present the message to the user,
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/// collect their input according to the requested schema, and return the result.
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///
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/// # Arguments
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/// * `request` - The elicitation request with message and schema
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/// * `context` - The request context
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///
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/// # Returns
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/// The user's response including action (accept/decline/cancel) and optional data
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///
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/// # Default Behavior
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/// The default implementation automatically declines all elicitation requests.
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/// Real clients should override this to provide user interaction.
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fn create_elicitation(
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&self,
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request: CreateElicitationRequestParam,
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context: RequestContext<RoleClient>,
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) -> impl Future<Output = Result<CreateElicitationResult, McpError>> + Send + '_ {
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// Default implementation declines all requests - real clients should override this
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let _ = (request, context);
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std::future::ready(Ok(CreateElicitationResult {
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action: ElicitationAction::Decline,
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content: None,
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}))
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}
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fn on_cancelled(
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&self,
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params: CancelledNotificationParam,
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@ -143,6 +143,7 @@ impl std::fmt::Display for ProtocolVersion {
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}
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impl ProtocolVersion {
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pub const V_2025_06_18: Self = Self(Cow::Borrowed("2025-06-18"));
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pub const V_2025_03_26: Self = Self(Cow::Borrowed("2025-03-26"));
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pub const V_2024_11_05: Self = Self(Cow::Borrowed("2024-11-05"));
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pub const LATEST: Self = Self::V_2025_03_26;
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@ -167,6 +168,7 @@ impl<'de> Deserialize<'de> for ProtocolVersion {
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match s.as_str() {
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"2024-11-05" => return Ok(ProtocolVersion::V_2024_11_05),
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"2025-03-26" => return Ok(ProtocolVersion::V_2025_03_26),
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"2025-06-18" => return Ok(ProtocolVersion::V_2025_06_18),
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_ => {}
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}
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Ok(ProtocolVersion(Cow::Owned(s)))
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@ -1173,6 +1175,75 @@ pub struct ListRootsResult {
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const_string!(RootsListChangedNotificationMethod = "notifications/roots/list_changed");
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pub type RootsListChangedNotification = NotificationNoParam<RootsListChangedNotificationMethod>;
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// =============================================================================
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// ELICITATION (INTERACTIVE USER INPUT)
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// =============================================================================
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// Method constants for elicitation operations.
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// Elicitation allows servers to request interactive input from users during tool execution.
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const_string!(ElicitationCreateRequestMethod = "elicitation/create");
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const_string!(ElicitationResponseNotificationMethod = "notifications/elicitation/response");
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/// Represents the possible actions a user can take in response to an elicitation request.
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///
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/// When a server requests user input through elicitation, the user can:
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/// - Accept: Provide the requested information and continue
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/// - Decline: Refuse to provide the information but continue the operation
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/// - Cancel: Stop the entire operation
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#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq)]
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#[serde(rename_all = "lowercase")]
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#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
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pub enum ElicitationAction {
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/// User accepts the request and provides the requested information
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Accept,
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/// User declines to provide the information but allows the operation to continue
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Decline,
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/// User cancels the entire operation
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Cancel,
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}
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/// Parameters for creating an elicitation request to gather user input.
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///
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/// This structure contains everything needed to request interactive input from a user:
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/// - A human-readable message explaining what information is needed
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/// - A JSON schema defining the expected structure of the response
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#[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
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#[serde(rename_all = "camelCase")]
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#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
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pub struct CreateElicitationRequestParam {
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/// Human-readable message explaining what input is needed from the user.
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/// This should be clear and provide sufficient context for the user to understand
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/// what information they need to provide.
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pub message: String,
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/// JSON Schema defining the expected structure and validation rules for the user's response.
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/// This allows clients to validate input and provide appropriate UI controls.
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/// Must be a valid JSON Schema Draft 2020-12 object.
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pub requested_schema: JsonObject,
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}
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/// The result returned by a client in response to an elicitation request.
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///
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/// Contains the user's decision (accept/decline/cancel) and optionally their input data
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/// if they chose to accept the request.
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#[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
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#[serde(rename_all = "camelCase")]
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#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
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pub struct CreateElicitationResult {
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/// The user's decision on how to handle the elicitation request
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pub action: ElicitationAction,
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/// The actual data provided by the user, if they accepted the request.
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/// Must conform to the JSON schema specified in the original request.
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/// Only present when action is Accept.
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#[serde(skip_serializing_if = "Option::is_none")]
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pub content: Option<Value>,
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}
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/// Request type for creating an elicitation to gather user input
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pub type CreateElicitationRequest =
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Request<ElicitationCreateRequestMethod, CreateElicitationRequestParam>;
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// =============================================================================
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// TOOL EXECUTION RESULTS
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// =============================================================================
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@ -1430,7 +1501,7 @@ ts_union!(
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);
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ts_union!(
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export type ClientResult = CreateMessageResult | ListRootsResult | EmptyResult;
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export type ClientResult = CreateMessageResult | ListRootsResult | CreateElicitationResult | EmptyResult;
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);
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impl ClientResult {
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@ -1445,7 +1516,8 @@ ts_union!(
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export type ServerRequest =
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| PingRequest
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| CreateMessageRequest
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| ListRootsRequest;
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| ListRootsRequest
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| CreateElicitationRequest;
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);
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ts_union!(
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@ -1470,6 +1542,7 @@ ts_union!(
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| ReadResourceResult
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| CallToolResult
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| ListToolsResult
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| CreateElicitationResult
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| EmptyResult
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;
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);
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@ -40,6 +40,22 @@ pub struct RootsCapabilities {
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pub list_changed: Option<bool>,
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}
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/// Capability for handling elicitation requests from servers.
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///
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/// Elicitation allows servers to request interactive input from users during tool execution.
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/// This capability indicates that a client can handle elicitation requests and present
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/// appropriate UI to users for collecting the requested information.
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#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Default)]
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#[serde(rename_all = "camelCase")]
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#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
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pub struct ElicitationCapability {
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/// Whether the client supports JSON Schema validation for elicitation responses.
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/// When true, the client will validate user input against the requested_schema
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/// before sending the response back to the server.
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#[serde(skip_serializing_if = "Option::is_none")]
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pub schema_validation: Option<bool>,
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}
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///
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/// # Builder
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/// ```rust
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@ -59,6 +75,9 @@ pub struct ClientCapabilities {
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pub roots: Option<RootsCapabilities>,
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#[serde(skip_serializing_if = "Option::is_none")]
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pub sampling: Option<JsonObject>,
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/// Capability to handle elicitation requests from servers for interactive user input
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#[serde(skip_serializing_if = "Option::is_none")]
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pub elicitation: Option<ElicitationCapability>,
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}
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///
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@ -253,6 +272,7 @@ builder! {
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experimental: ExperimentalCapabilities,
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roots: RootsCapabilities,
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sampling: JsonObject,
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elicitation: ElicitationCapability,
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}
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}
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@ -267,6 +287,21 @@ impl<const E: bool, const S: bool>
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}
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}
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#[cfg(feature = "elicitation")]
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impl<const E: bool, const R: bool, const S: bool>
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ClientCapabilitiesBuilder<ClientCapabilitiesBuilderState<E, R, S, true>>
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{
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/// Enable JSON Schema validation for elicitation responses.
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/// When enabled, the client will validate user input against the requested_schema
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/// before sending responses back to the server.
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pub fn enable_elicitation_schema_validation(mut self) -> Self {
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if let Some(c) = self.elicitation.as_mut() {
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c.schema_validation = Some(true);
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}
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self
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}
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}
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#[cfg(test)]
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mod test {
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use super::*;
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@ -74,6 +74,7 @@ variant_extension! {
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PingRequest
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CreateMessageRequest
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ListRootsRequest
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CreateElicitationRequest
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}
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}
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@ -3,6 +3,10 @@ use std::borrow::Cow;
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use thiserror::Error;
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use super::*;
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#[cfg(feature = "elicitation")]
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use crate::model::{
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CreateElicitationRequest, CreateElicitationRequestParam, CreateElicitationResult,
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};
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use crate::{
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model::{
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CancelledNotification, CancelledNotificationParam, ClientInfo, ClientJsonRpcMessage,
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@ -324,11 +328,68 @@ macro_rules! method {
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Ok(())
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}
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};
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// Timeout-only variants (base method should be created separately with peer_req)
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(peer_req_with_timeout $method_with_timeout:ident $Req:ident() => $Resp: ident) => {
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pub async fn $method_with_timeout(
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&self,
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timeout: Option<std::time::Duration>,
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) -> Result<$Resp, ServiceError> {
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let request = ServerRequest::$Req($Req {
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method: Default::default(),
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extensions: Default::default(),
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});
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let options = crate::service::PeerRequestOptions {
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timeout,
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meta: None,
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};
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let result = self
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.send_request_with_option(request, options)
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.await?
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.await_response()
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.await?;
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match result {
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ClientResult::$Resp(result) => Ok(result),
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_ => Err(ServiceError::UnexpectedResponse),
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}
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}
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};
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(peer_req_with_timeout $method_with_timeout:ident $Req:ident($Param: ident) => $Resp: ident) => {
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pub async fn $method_with_timeout(
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&self,
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params: $Param,
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timeout: Option<std::time::Duration>,
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) -> Result<$Resp, ServiceError> {
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let request = ServerRequest::$Req($Req {
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method: Default::default(),
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params,
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extensions: Default::default(),
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});
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let options = crate::service::PeerRequestOptions {
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timeout,
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meta: None,
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};
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let result = self
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.send_request_with_option(request, options)
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.await?
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.await_response()
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.await?;
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match result {
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ClientResult::$Resp(result) => Ok(result),
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_ => Err(ServiceError::UnexpectedResponse),
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}
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}
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};
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}
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impl Peer<RoleServer> {
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method!(peer_req create_message CreateMessageRequest(CreateMessageRequestParam) => CreateMessageResult);
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method!(peer_req list_roots ListRootsRequest() => ListRootsResult);
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#[cfg(feature = "elicitation")]
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method!(peer_req create_elicitation CreateElicitationRequest(CreateElicitationRequestParam) => CreateElicitationResult);
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#[cfg(feature = "elicitation")]
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method!(peer_req_with_timeout create_elicitation_with_timeout CreateElicitationRequest(CreateElicitationRequestParam) => CreateElicitationResult);
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method!(peer_not notify_cancelled CancelledNotification(CancelledNotificationParam));
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method!(peer_not notify_progress ProgressNotification(ProgressNotificationParam));
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method!(peer_not notify_tool_list_changed ToolListChangedNotification);
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method!(peer_not notify_prompt_list_changed PromptListChangedNotification);
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}
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// =============================================================================
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// ELICITATION CONVENIENCE METHODS
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// These methods are specific to server role and provide typed elicitation functionality
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// =============================================================================
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/// Errors that can occur during typed elicitation operations
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#[cfg(feature = "elicitation")]
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#[derive(Error, Debug)]
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pub enum ElicitationError {
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/// The elicitation request failed at the service level
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#[error("Service error: {0}")]
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Service(#[from] ServiceError),
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/// User explicitly declined to provide the requested information
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/// This indicates a conscious decision by the user to reject the request
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/// (e.g., clicked "Reject", "Decline", "No", etc.)
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#[error("User explicitly declined the request")]
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UserDeclined,
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/// User dismissed the request without making an explicit choice
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/// This indicates the user cancelled without explicitly declining
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/// (e.g., closed dialog, clicked outside, pressed Escape, etc.)
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#[error("User cancelled/dismissed the request")]
|
||||
UserCancelled,
|
||||
|
||||
/// The response data could not be parsed into the requested type
|
||||
#[error("Failed to parse response data: {error}\nReceived data: {data}")]
|
||||
ParseError {
|
||||
error: serde_json::Error,
|
||||
data: serde_json::Value,
|
||||
},
|
||||
|
||||
/// No response content was provided by the user
|
||||
#[error("No response content provided")]
|
||||
NoContent,
|
||||
|
||||
/// Client does not support elicitation capability
|
||||
#[error("Client does not support elicitation - capability not declared during initialization")]
|
||||
CapabilityNotSupported,
|
||||
}
|
||||
|
||||
/// Marker trait to ensure that elicitation types generate object-type JSON schemas.
|
||||
///
|
||||
/// This trait provides compile-time safety to ensure that types used with
|
||||
/// `elicit<T>()` methods will generate JSON schemas of type "object", which
|
||||
/// aligns with MCP client expectations for structured data input.
|
||||
///
|
||||
/// # Type Safety Rationale
|
||||
///
|
||||
/// MCP clients typically expect JSON objects for elicitation schemas to
|
||||
/// provide structured forms and validation. This trait prevents common
|
||||
/// mistakes like:
|
||||
///
|
||||
/// ```compile_fail
|
||||
/// // These would not compile due to missing ElicitationSafe bound:
|
||||
/// let name: String = server.elicit("Enter name").await?; // Primitive
|
||||
/// let items: Vec<i32> = server.elicit("Enter items").await?; // Array
|
||||
/// ```
|
||||
#[cfg(feature = "elicitation")]
|
||||
pub trait ElicitationSafe: schemars::JsonSchema {}
|
||||
|
||||
/// Macro to mark types as safe for elicitation by verifying they generate object schemas.
|
||||
///
|
||||
/// This macro automatically implements the `ElicitationSafe` trait for struct types
|
||||
/// that should be used with `elicit<T>()` methods.
|
||||
///
|
||||
/// # Example
|
||||
///
|
||||
/// ```rust
|
||||
/// use rmcp::elicit_safe;
|
||||
/// use schemars::JsonSchema;
|
||||
/// use serde::{Deserialize, Serialize};
|
||||
///
|
||||
/// #[derive(Serialize, Deserialize, JsonSchema)]
|
||||
/// struct UserProfile {
|
||||
/// name: String,
|
||||
/// email: String,
|
||||
/// }
|
||||
///
|
||||
/// elicit_safe!(UserProfile);
|
||||
///
|
||||
/// // Now safe to use in async context:
|
||||
/// // let profile: UserProfile = server.elicit("Enter profile").await?;
|
||||
/// ```
|
||||
#[cfg(feature = "elicitation")]
|
||||
#[macro_export]
|
||||
macro_rules! elicit_safe {
|
||||
($($t:ty),* $(,)?) => {
|
||||
$(
|
||||
impl $crate::service::ElicitationSafe for $t {}
|
||||
)*
|
||||
};
|
||||
}
|
||||
|
||||
#[cfg(feature = "elicitation")]
|
||||
impl Peer<RoleServer> {
|
||||
/// Check if the client supports elicitation capability
|
||||
///
|
||||
/// Returns true if the client declared elicitation capability during initialization,
|
||||
/// false otherwise. According to MCP 2025-06-18 specification, clients that support
|
||||
/// elicitation MUST declare the capability during initialization.
|
||||
pub fn supports_elicitation(&self) -> bool {
|
||||
if let Some(client_info) = self.peer_info() {
|
||||
client_info.capabilities.elicitation.is_some()
|
||||
} else {
|
||||
false
|
||||
}
|
||||
}
|
||||
|
||||
/// Request typed data from the user with automatic schema generation.
|
||||
///
|
||||
/// This method automatically generates the JSON schema from the Rust type using `schemars`,
|
||||
/// eliminating the need to manually create schemas. The response is automatically parsed
|
||||
/// into the requested type.
|
||||
///
|
||||
/// **Requires the `elicitation` feature to be enabled.**
|
||||
///
|
||||
/// # Type Requirements
|
||||
/// The type `T` must implement:
|
||||
/// - `schemars::JsonSchema` - for automatic schema generation
|
||||
/// - `serde::Deserialize` - for parsing the response
|
||||
///
|
||||
/// # Arguments
|
||||
/// * `message` - The prompt message for the user
|
||||
///
|
||||
/// # Returns
|
||||
/// * `Ok(Some(data))` if user provided valid data that matches type T
|
||||
/// * `Err(ElicitationError::UserDeclined)` if user explicitly declined the request
|
||||
/// * `Err(ElicitationError::UserCancelled)` if user cancelled/dismissed the request
|
||||
/// * `Err(ElicitationError::ParseError { .. })` if response data couldn't be parsed into type T
|
||||
/// * `Err(ElicitationError::NoContent)` if no response content was provided
|
||||
/// * `Err(ElicitationError::Service(_))` if the underlying service call failed
|
||||
///
|
||||
/// # Example
|
||||
///
|
||||
/// Add to your `Cargo.toml`:
|
||||
/// ```toml
|
||||
/// [dependencies]
|
||||
/// rmcp = { version = "0.3", features = ["elicitation"] }
|
||||
/// serde = { version = "1.0", features = ["derive"] }
|
||||
/// schemars = "1.0"
|
||||
/// ```
|
||||
///
|
||||
/// ```rust,no_run
|
||||
/// # use rmcp::*;
|
||||
/// # use rmcp::service::ElicitationError;
|
||||
/// # use serde::{Deserialize, Serialize};
|
||||
/// # use schemars::JsonSchema;
|
||||
/// #
|
||||
/// #[derive(Debug, Serialize, Deserialize, JsonSchema)]
|
||||
/// struct UserProfile {
|
||||
/// #[schemars(description = "Full name")]
|
||||
/// name: String,
|
||||
/// #[schemars(description = "Email address")]
|
||||
/// email: String,
|
||||
/// #[schemars(description = "Age")]
|
||||
/// age: u8,
|
||||
/// }
|
||||
///
|
||||
/// // Mark as safe for elicitation (generates object schema)
|
||||
/// rmcp::elicit_safe!(UserProfile);
|
||||
///
|
||||
/// # async fn example(peer: Peer<RoleServer>) -> Result<(), Box<dyn std::error::Error>> {
|
||||
/// match peer.elicit::<UserProfile>("Please enter your profile information").await {
|
||||
/// Ok(Some(profile)) => {
|
||||
/// println!("Name: {}, Email: {}, Age: {}", profile.name, profile.email, profile.age);
|
||||
/// }
|
||||
/// Ok(None) => {
|
||||
/// println!("User provided no content");
|
||||
/// }
|
||||
/// Err(ElicitationError::UserDeclined) => {
|
||||
/// println!("User explicitly declined to provide information");
|
||||
/// // Handle explicit decline - perhaps offer alternatives
|
||||
/// }
|
||||
/// Err(ElicitationError::UserCancelled) => {
|
||||
/// println!("User cancelled the request");
|
||||
/// // Handle cancellation - perhaps prompt again later
|
||||
/// }
|
||||
/// Err(ElicitationError::ParseError { error, data }) => {
|
||||
/// println!("Failed to parse response: {}\nData: {}", error, data);
|
||||
/// }
|
||||
/// Err(e) => return Err(e.into()),
|
||||
/// }
|
||||
/// # Ok(())
|
||||
/// # }
|
||||
/// ```
|
||||
#[cfg(all(feature = "schemars", feature = "elicitation"))]
|
||||
pub async fn elicit<T>(&self, message: impl Into<String>) -> Result<Option<T>, ElicitationError>
|
||||
where
|
||||
T: ElicitationSafe + for<'de> serde::Deserialize<'de>,
|
||||
{
|
||||
self.elicit_with_timeout(message, None).await
|
||||
}
|
||||
|
||||
/// Request typed data from the user with custom timeout.
|
||||
///
|
||||
/// Same as `elicit()` but allows specifying a custom timeout for the request.
|
||||
/// If the user doesn't respond within the timeout, the request will be cancelled.
|
||||
///
|
||||
/// # Arguments
|
||||
/// * `message` - The prompt message for the user
|
||||
/// * `timeout` - Optional timeout duration. If None, uses default timeout behavior
|
||||
///
|
||||
/// # Returns
|
||||
/// Same as `elicit()` but may also return `ServiceError::Timeout` if timeout expires
|
||||
///
|
||||
/// # Example
|
||||
/// ```rust,no_run
|
||||
/// # use rmcp::*;
|
||||
/// # use rmcp::service::ElicitationError;
|
||||
/// # use serde::{Deserialize, Serialize};
|
||||
/// # use schemars::JsonSchema;
|
||||
/// # use std::time::Duration;
|
||||
/// #
|
||||
/// #[derive(Debug, Serialize, Deserialize, JsonSchema)]
|
||||
/// struct QuickResponse {
|
||||
/// answer: String,
|
||||
/// }
|
||||
///
|
||||
/// // Mark as safe for elicitation
|
||||
/// rmcp::elicit_safe!(QuickResponse);
|
||||
///
|
||||
/// # async fn example(peer: Peer<RoleServer>) -> Result<(), Box<dyn std::error::Error>> {
|
||||
/// // Give user 30 seconds to respond
|
||||
/// let timeout = Some(Duration::from_secs(30));
|
||||
/// match peer.elicit_with_timeout::<QuickResponse>(
|
||||
/// "Quick question - what's your answer?",
|
||||
/// timeout
|
||||
/// ).await {
|
||||
/// Ok(Some(response)) => println!("Got answer: {}", response.answer),
|
||||
/// Ok(None) => println!("User provided no content"),
|
||||
/// Err(ElicitationError::UserDeclined) => {
|
||||
/// println!("User explicitly declined");
|
||||
/// // Handle explicit decline
|
||||
/// }
|
||||
/// Err(ElicitationError::UserCancelled) => {
|
||||
/// println!("User cancelled/dismissed");
|
||||
/// // Handle cancellation
|
||||
/// }
|
||||
/// Err(ElicitationError::Service(ServiceError::Timeout { .. })) => {
|
||||
/// println!("User didn't respond in time");
|
||||
/// }
|
||||
/// Err(e) => return Err(e.into()),
|
||||
/// }
|
||||
/// # Ok(())
|
||||
/// # }
|
||||
/// ```
|
||||
#[cfg(all(feature = "schemars", feature = "elicitation"))]
|
||||
pub async fn elicit_with_timeout<T>(
|
||||
&self,
|
||||
message: impl Into<String>,
|
||||
timeout: Option<std::time::Duration>,
|
||||
) -> Result<Option<T>, ElicitationError>
|
||||
where
|
||||
T: ElicitationSafe + for<'de> serde::Deserialize<'de>,
|
||||
{
|
||||
// Check if client supports elicitation capability
|
||||
if !self.supports_elicitation() {
|
||||
return Err(ElicitationError::CapabilityNotSupported);
|
||||
}
|
||||
|
||||
// Generate schema automatically from type
|
||||
let schema = crate::handler::server::tool::schema_for_type::<T>();
|
||||
|
||||
let response = self
|
||||
.create_elicitation_with_timeout(
|
||||
CreateElicitationRequestParam {
|
||||
message: message.into(),
|
||||
requested_schema: schema,
|
||||
},
|
||||
timeout,
|
||||
)
|
||||
.await?;
|
||||
|
||||
match response.action {
|
||||
crate::model::ElicitationAction::Accept => {
|
||||
if let Some(value) = response.content {
|
||||
match serde_json::from_value::<T>(value.clone()) {
|
||||
Ok(parsed) => Ok(Some(parsed)),
|
||||
Err(error) => Err(ElicitationError::ParseError { error, data: value }),
|
||||
}
|
||||
} else {
|
||||
Err(ElicitationError::NoContent)
|
||||
}
|
||||
}
|
||||
crate::model::ElicitationAction::Decline => Err(ElicitationError::UserDeclined),
|
||||
crate::model::ElicitationAction::Cancel => Err(ElicitationError::UserCancelled),
|
||||
}
|
||||
}
|
||||
}
|
||||
|
|
|
|||
1466
crates/rmcp/tests/test_elicitation.rs
Normal file
1466
crates/rmcp/tests/test_elicitation.rs
Normal file
File diff suppressed because it is too large
Load diff
|
|
@ -257,6 +257,17 @@
|
|||
"description": "```rust\n# use rmcp::model::ClientCapabilities;\nlet cap = ClientCapabilities::builder()\n .enable_experimental()\n .enable_roots()\n .enable_roots_list_changed()\n .build();\n```",
|
||||
"type": "object",
|
||||
"properties": {
|
||||
"elicitation": {
|
||||
"description": "Capability to handle elicitation requests from servers for interactive user input",
|
||||
"anyOf": [
|
||||
{
|
||||
"$ref": "#/definitions/ElicitationCapability"
|
||||
},
|
||||
{
|
||||
"type": "null"
|
||||
}
|
||||
]
|
||||
},
|
||||
"experimental": {
|
||||
"type": [
|
||||
"object",
|
||||
|
|
@ -294,6 +305,9 @@
|
|||
{
|
||||
"$ref": "#/definitions/ListRootsResult"
|
||||
},
|
||||
{
|
||||
"$ref": "#/definitions/CreateElicitationResult"
|
||||
},
|
||||
{
|
||||
"$ref": "#/definitions/EmptyObject"
|
||||
}
|
||||
|
|
@ -319,6 +333,26 @@
|
|||
"argument"
|
||||
]
|
||||
},
|
||||
"CreateElicitationResult": {
|
||||
"description": "The result returned by a client in response to an elicitation request.\n\nContains the user's decision (accept/decline/cancel) and optionally their input data\nif they chose to accept the request.",
|
||||
"type": "object",
|
||||
"properties": {
|
||||
"action": {
|
||||
"description": "The user's decision on how to handle the elicitation request",
|
||||
"allOf": [
|
||||
{
|
||||
"$ref": "#/definitions/ElicitationAction"
|
||||
}
|
||||
]
|
||||
},
|
||||
"content": {
|
||||
"description": "The actual data provided by the user, if they accepted the request.\nMust conform to the JSON schema specified in the original request.\nOnly present when action is Accept."
|
||||
}
|
||||
},
|
||||
"required": [
|
||||
"action"
|
||||
]
|
||||
},
|
||||
"CreateMessageResult": {
|
||||
"description": "The result of a sampling/createMessage request containing the generated response.\n\nThis structure contains the generated message along with metadata about\nhow the generation was performed and why it stopped.",
|
||||
"type": "object",
|
||||
|
|
@ -357,6 +391,39 @@
|
|||
"content"
|
||||
]
|
||||
},
|
||||
"ElicitationAction": {
|
||||
"description": "Represents the possible actions a user can take in response to an elicitation request.\n\nWhen a server requests user input through elicitation, the user can:\n- Accept: Provide the requested information and continue\n- Decline: Refuse to provide the information but continue the operation\n- Cancel: Stop the entire operation",
|
||||
"oneOf": [
|
||||
{
|
||||
"description": "User accepts the request and provides the requested information",
|
||||
"type": "string",
|
||||
"const": "accept"
|
||||
},
|
||||
{
|
||||
"description": "User declines to provide the information but allows the operation to continue",
|
||||
"type": "string",
|
||||
"const": "decline"
|
||||
},
|
||||
{
|
||||
"description": "User cancels the entire operation",
|
||||
"type": "string",
|
||||
"const": "cancel"
|
||||
}
|
||||
]
|
||||
},
|
||||
"ElicitationCapability": {
|
||||
"description": "Capability for handling elicitation requests from servers.\n\nElicitation allows servers to request interactive input from users during tool execution.\nThis capability indicates that a client can handle elicitation requests and present\nappropriate UI to users for collecting the requested information.",
|
||||
"type": "object",
|
||||
"properties": {
|
||||
"schemaValidation": {
|
||||
"description": "Whether the client supports JSON Schema validation for elicitation responses.\nWhen true, the client will validate user input against the requested_schema\nbefore sending the response back to the server.",
|
||||
"type": [
|
||||
"boolean",
|
||||
"null"
|
||||
]
|
||||
}
|
||||
}
|
||||
},
|
||||
"EmptyObject": {
|
||||
"description": "This is commonly used for representing empty objects in MCP messages.\n\nwithout returning any specific data.",
|
||||
"type": "object"
|
||||
|
|
|
|||
|
|
@ -405,6 +405,45 @@
|
|||
}
|
||||
]
|
||||
},
|
||||
"CreateElicitationRequestParam": {
|
||||
"description": "Parameters for creating an elicitation request to gather user input.\n\nThis structure contains everything needed to request interactive input from a user:\n- A human-readable message explaining what information is needed\n- A JSON schema defining the expected structure of the response",
|
||||
"type": "object",
|
||||
"properties": {
|
||||
"message": {
|
||||
"description": "Human-readable message explaining what input is needed from the user.\nThis should be clear and provide sufficient context for the user to understand\nwhat information they need to provide.",
|
||||
"type": "string"
|
||||
},
|
||||
"requestedSchema": {
|
||||
"description": "JSON Schema defining the expected structure and validation rules for the user's response.\nThis allows clients to validate input and provide appropriate UI controls.\nMust be a valid JSON Schema Draft 2020-12 object.",
|
||||
"type": "object",
|
||||
"additionalProperties": true
|
||||
}
|
||||
},
|
||||
"required": [
|
||||
"message",
|
||||
"requestedSchema"
|
||||
]
|
||||
},
|
||||
"CreateElicitationResult": {
|
||||
"description": "The result returned by a client in response to an elicitation request.\n\nContains the user's decision (accept/decline/cancel) and optionally their input data\nif they chose to accept the request.",
|
||||
"type": "object",
|
||||
"properties": {
|
||||
"action": {
|
||||
"description": "The user's decision on how to handle the elicitation request",
|
||||
"allOf": [
|
||||
{
|
||||
"$ref": "#/definitions/ElicitationAction"
|
||||
}
|
||||
]
|
||||
},
|
||||
"content": {
|
||||
"description": "The actual data provided by the user, if they accepted the request.\nMust conform to the JSON schema specified in the original request.\nOnly present when action is Accept."
|
||||
}
|
||||
},
|
||||
"required": [
|
||||
"action"
|
||||
]
|
||||
},
|
||||
"CreateMessageRequestMethod": {
|
||||
"type": "string",
|
||||
"format": "const",
|
||||
|
|
@ -483,6 +522,31 @@
|
|||
"maxTokens"
|
||||
]
|
||||
},
|
||||
"ElicitationAction": {
|
||||
"description": "Represents the possible actions a user can take in response to an elicitation request.\n\nWhen a server requests user input through elicitation, the user can:\n- Accept: Provide the requested information and continue\n- Decline: Refuse to provide the information but continue the operation\n- Cancel: Stop the entire operation",
|
||||
"oneOf": [
|
||||
{
|
||||
"description": "User accepts the request and provides the requested information",
|
||||
"type": "string",
|
||||
"const": "accept"
|
||||
},
|
||||
{
|
||||
"description": "User declines to provide the information but allows the operation to continue",
|
||||
"type": "string",
|
||||
"const": "decline"
|
||||
},
|
||||
{
|
||||
"description": "User cancels the entire operation",
|
||||
"type": "string",
|
||||
"const": "cancel"
|
||||
}
|
||||
]
|
||||
},
|
||||
"ElicitationCreateRequestMethod": {
|
||||
"type": "string",
|
||||
"format": "const",
|
||||
"const": "elicitation/create"
|
||||
},
|
||||
"EmptyObject": {
|
||||
"description": "This is commonly used for representing empty objects in MCP messages.\n\nwithout returning any specific data.",
|
||||
"type": "object"
|
||||
|
|
@ -686,6 +750,9 @@
|
|||
},
|
||||
{
|
||||
"$ref": "#/definitions/RequestNoParam2"
|
||||
},
|
||||
{
|
||||
"$ref": "#/definitions/Request2"
|
||||
}
|
||||
],
|
||||
"required": [
|
||||
|
|
@ -1307,6 +1374,22 @@
|
|||
"params"
|
||||
]
|
||||
},
|
||||
"Request2": {
|
||||
"description": "Represents a JSON-RPC request with method, parameters, and extensions.\n\nThis is the core structure for all MCP requests, containing:\n- `method`: The name of the method being called\n- `params`: The parameters for the method\n- `extensions`: Additional context data (similar to HTTP headers)",
|
||||
"type": "object",
|
||||
"properties": {
|
||||
"method": {
|
||||
"$ref": "#/definitions/ElicitationCreateRequestMethod"
|
||||
},
|
||||
"params": {
|
||||
"$ref": "#/definitions/CreateElicitationRequestParam"
|
||||
}
|
||||
},
|
||||
"required": [
|
||||
"method",
|
||||
"params"
|
||||
]
|
||||
},
|
||||
"RequestNoParam": {
|
||||
"type": "object",
|
||||
"properties": {
|
||||
|
|
@ -1546,6 +1629,9 @@
|
|||
{
|
||||
"$ref": "#/definitions/ListToolsResult"
|
||||
},
|
||||
{
|
||||
"$ref": "#/definitions/CreateElicitationResult"
|
||||
},
|
||||
{
|
||||
"$ref": "#/definitions/EmptyObject"
|
||||
}
|
||||
|
|
|
|||
|
|
@ -14,6 +14,8 @@ rmcp = { workspace = true, features = [
|
|||
"transport-io",
|
||||
"transport-streamable-http-server",
|
||||
"auth",
|
||||
"elicitation",
|
||||
"schemars",
|
||||
] }
|
||||
tokio = { version = "1", features = [
|
||||
"macros",
|
||||
|
|
@ -34,7 +36,7 @@ tracing-subscriber = { version = "0.3", features = [
|
|||
futures = "0.3"
|
||||
rand = { version = "0.9", features = ["std"] }
|
||||
axum = { version = "0.8", features = ["macros"] }
|
||||
schemars = { version = "1.0" }
|
||||
schemars = "1.0"
|
||||
reqwest = { version = "0.12", features = ["json"] }
|
||||
chrono = "0.4"
|
||||
uuid = { version = "1.6", features = ["v4", "serde"] }
|
||||
|
|
@ -87,3 +89,7 @@ path = "src/sampling_stdio.rs"
|
|||
[[example]]
|
||||
name = "servers_structured_output"
|
||||
path = "src/structured_output.rs"
|
||||
|
||||
[[example]]
|
||||
name = "servers_elicitation_stdio"
|
||||
path = "src/elicitation_stdio.rs"
|
||||
|
|
|
|||
|
|
@ -47,6 +47,7 @@ A server using streamable HTTP transport for MCP communication, with axum.
|
|||
### Counter Streamable HTTP Server with Hyper (`counter_hyper_streamable_http.rs`)
|
||||
|
||||
A server using streamable HTTP transport for MCP communication, with hyper.
|
||||
|
||||
- Runs on HTTP with streaming capabilities
|
||||
- Provides counter tools via HTTP streaming
|
||||
- Demonstrates streamable HTTP transport configuration
|
||||
|
|
@ -72,6 +73,16 @@ A simplified OAuth example showing basic token-based authentication.
|
|||
- Simplified authentication flow
|
||||
- Good starting point for adding authentication to MCP servers
|
||||
|
||||
### Elicitation Demo (`elicitation_stdio.rs`)
|
||||
|
||||
A working MCP server demonstrating elicitation for user name collection.
|
||||
|
||||
- Real MCP server using rmcp library
|
||||
- `context.peer.elicit::<T>()` API usage
|
||||
- Type-safe elicitation with `elicit_safe!` macro
|
||||
- JSON Schema validation with schemars
|
||||
- Tools: `greet_user` (collects name), `reset_name` (clears stored name)
|
||||
|
||||
## How to Run
|
||||
|
||||
Each example can be run using Cargo:
|
||||
|
|
@ -97,6 +108,9 @@ cargo run --example servers_complex_auth_sse
|
|||
|
||||
# Run the simple OAuth SSE server
|
||||
cargo run --example servers_simple_auth_sse
|
||||
|
||||
# Run the elicitation standard I/O server
|
||||
cargo run --example servers_elicitation_stdio
|
||||
```
|
||||
|
||||
## Testing with MCP Inspector
|
||||
|
|
@ -120,6 +134,7 @@ These examples use the following main dependencies:
|
|||
- `uuid`: UUID generation (used in OAuth examples)
|
||||
- `chrono`: Date and time handling (used in OAuth examples)
|
||||
- `rand`: Random number generation (used in OAuth examples)
|
||||
- `schemars`: JSON Schema generation (used in elicitation examples)
|
||||
|
||||
## Common Module
|
||||
|
||||
|
|
@ -129,4 +144,4 @@ The `common/` directory contains shared code used across examples:
|
|||
- `calculator.rs`: Calculator tool examples
|
||||
- `generic_service.rs`: Generic service implementations
|
||||
|
||||
This modular approach allows for code reuse and demonstrates how to structure larger MCP server applications.
|
||||
This modular approach allows for code reuse and demonstrates how to structure larger MCP server applications.
|
||||
|
|
|
|||
143
examples/servers/src/elicitation_stdio.rs
Normal file
143
examples/servers/src/elicitation_stdio.rs
Normal file
|
|
@ -0,0 +1,143 @@
|
|||
//! Simple MCP Server with Elicitation
|
||||
//!
|
||||
//! Demonstrates user name collection via elicitation
|
||||
|
||||
use std::sync::Arc;
|
||||
|
||||
use anyhow::Result;
|
||||
use rmcp::{
|
||||
ErrorData as McpError, ServerHandler, ServiceExt, elicit_safe,
|
||||
handler::server::{router::tool::ToolRouter, tool::Parameters},
|
||||
model::*,
|
||||
schemars::JsonSchema,
|
||||
service::{RequestContext, RoleServer},
|
||||
tool, tool_handler, tool_router,
|
||||
transport::stdio,
|
||||
};
|
||||
use serde::{Deserialize, Serialize};
|
||||
use tokio::sync::Mutex;
|
||||
use tracing_subscriber::{self, EnvFilter};
|
||||
|
||||
/// User information request
|
||||
#[derive(Debug, Serialize, Deserialize, JsonSchema)]
|
||||
#[schemars(description = "User information")]
|
||||
pub struct UserInfo {
|
||||
#[schemars(description = "User's name")]
|
||||
pub name: String,
|
||||
}
|
||||
|
||||
// Mark as safe for elicitation
|
||||
elicit_safe!(UserInfo);
|
||||
|
||||
/// Simple tool request
|
||||
#[derive(Debug, Deserialize, JsonSchema)]
|
||||
pub struct GreetRequest {
|
||||
pub greeting: String,
|
||||
}
|
||||
|
||||
/// Simple server with elicitation
|
||||
#[derive(Clone)]
|
||||
pub struct ElicitationServer {
|
||||
user_name: Arc<Mutex<Option<String>>>,
|
||||
tool_router: ToolRouter<ElicitationServer>,
|
||||
}
|
||||
|
||||
impl Default for ElicitationServer {
|
||||
fn default() -> Self {
|
||||
Self::new()
|
||||
}
|
||||
}
|
||||
|
||||
#[tool_router]
|
||||
impl ElicitationServer {
|
||||
pub fn new() -> Self {
|
||||
Self {
|
||||
user_name: Arc::new(Mutex::new(None)),
|
||||
tool_router: Self::tool_router(),
|
||||
}
|
||||
}
|
||||
|
||||
#[tool(description = "Greet user with name collection")]
|
||||
async fn greet_user(
|
||||
&self,
|
||||
context: RequestContext<RoleServer>,
|
||||
Parameters(request): Parameters<GreetRequest>,
|
||||
) -> Result<CallToolResult, McpError> {
|
||||
// Check if we have user name
|
||||
let current_name = self.user_name.lock().await.clone();
|
||||
|
||||
let user_name = if let Some(name) = current_name {
|
||||
name
|
||||
} else {
|
||||
// Request user name via elicitation
|
||||
match context
|
||||
.peer
|
||||
.elicit::<UserInfo>("Please provide your name".to_string())
|
||||
.await
|
||||
{
|
||||
Ok(Some(user_info)) => {
|
||||
let name = user_info.name.clone();
|
||||
*self.user_name.lock().await = Some(name.clone());
|
||||
name
|
||||
}
|
||||
Ok(None) => "Guest".to_string(), // Never happen if client checks schema
|
||||
Err(_) => "Unknown".to_string(),
|
||||
}
|
||||
};
|
||||
|
||||
Ok(CallToolResult::success(vec![Content::text(format!(
|
||||
"{} {}!",
|
||||
request.greeting, user_name
|
||||
))]))
|
||||
}
|
||||
|
||||
#[tool(description = "Reset stored user name")]
|
||||
async fn reset_name(&self) -> Result<CallToolResult, McpError> {
|
||||
*self.user_name.lock().await = None;
|
||||
Ok(CallToolResult::success(vec![Content::text(
|
||||
"User name reset. Next greeting will ask for name again.".to_string(),
|
||||
)]))
|
||||
}
|
||||
}
|
||||
|
||||
#[tool_handler]
|
||||
impl ServerHandler for ElicitationServer {
|
||||
fn get_info(&self) -> ServerInfo {
|
||||
ServerInfo {
|
||||
capabilities: ServerCapabilities::builder().enable_tools().build(),
|
||||
server_info: Implementation::from_build_env(),
|
||||
instructions: Some(
|
||||
"Simple server demonstrating elicitation for user name collection".to_string(),
|
||||
),
|
||||
..Default::default()
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
#[tokio::main]
|
||||
async fn main() -> Result<()> {
|
||||
tracing_subscriber::fmt()
|
||||
.with_env_filter(EnvFilter::from_default_env())
|
||||
.init();
|
||||
|
||||
println!("Simple MCP Elicitation Demo");
|
||||
|
||||
// Get current executable path for Inspector
|
||||
let current_exe = std::env::current_exe()
|
||||
.map(|path| path.display().to_string())
|
||||
.unwrap();
|
||||
|
||||
println!("To test with MCP Inspector:");
|
||||
println!("1. Run: npx @modelcontextprotocol/inspector");
|
||||
println!("2. Enter server command: {}", current_exe);
|
||||
|
||||
let service = ElicitationServer::new()
|
||||
.serve(stdio())
|
||||
.await
|
||||
.inspect_err(|e| {
|
||||
tracing::error!("serving error: {:?}", e);
|
||||
})?;
|
||||
|
||||
service.waiting().await?;
|
||||
Ok(())
|
||||
}
|
||||
Loading…
Reference in a new issue