feat: Add support for Tool.outputSchema and CallToolResult.structuredContent (#316)
* feat: add output_schema field to Tool struct - Add optional output_schema field to Tool struct for defining tool output structure - Update Tool::new() to initialize output_schema as None * feat: add structured_content field to CallToolResult - Add optional structured_content field for JSON object results - Make content field optional to support either structured or unstructured results - Add CallToolResult::structured() and structured_error() constructor methods * feat: implement validation for mutually exclusive content/structuredContent - Add validate() method to ensure content and structured_content are mutually exclusive - Implement custom Deserialize to enforce validation during deserialization - Update documentation to clarify the mutual exclusivity requirement * feat: add output_schema support to #[tool] macro - Add output_schema field to ToolAttribute and ResolvedToolAttribute structs - Implement automatic output schema generation from return types - Support explicit output_schema attribute for manual specification - Generate schemas for Result<T, E> where T is not CallToolResult - Update tool generation to include output_schema in Tool struct * feat: implement IntoCallToolResult for structured content - Add Structured<T> wrapper type for explicit structured content - Implement IntoCallToolResult for Structured<T> with JSON serialization - Add support for Result<Structured<T>, E> conversions - Enable tools to return structured content through the trait system * fix: update simple-chat-client example for optional content field - Handle Option<Vec<Content>> in CallToolResult.content - Add proper unwrapping for the optional content field - Fix compilation error in chat.rs * fix: update examples and tests for optional content field - Add output_schema field to Tool initialization in sampling_stdio example - Update test_tool_macros tests to handle Option<Vec<Content>> - Use as_ref() before calling first() on optional content field * feat: implement basic schema validation in conversion logic - Add validate_against_schema function for basic type validation - Add note that full JSON Schema validation requires dedicated library - Document that actual validation should happen in tool handler * feat: add structured output support for tools - Add output_schema field to Tool struct for defining output JSON schemas - Add structured_content field to CallToolResult (mutually exclusive with content) - Implement Structured<T> wrapper for type-safe structured outputs - Update #[tool] macro to automatically generate output schemas from return types - Add validation of structured outputs against their schemas - Update all examples and tests for breaking change (CallToolResult.content now Option) - Add comprehensive documentation and rustdoc - Add structured_output example demonstrating the feature BREAKING CHANGE: CallToolResult.content is now Option<Vec<Content>> instead of Vec<Content> Closes #312 * fix: correct structured output doctest to use Parameters wrapper The #[tool] macro requires Parameters<T> wrapper for tool inputs. This fixes the pre-existing broken doctest in the structured output documentation example. * feat: replace Structured<T> with Json<T> for structured output - Remove Structured<T> type definition and implementations - Reuse existing Json<T> wrapper for structured content - Update IntoCallToolResult implementations to use Json<T> - Add JsonSchema implementation for Json<T> delegating to T - Update all examples and tests to use Json<T> instead of Structured<T> - Update documentation and exports BREAKING CHANGE: Structured<T> has been replaced with Json<T>. Users must update their code to use Json<T> for structured tool outputs. * feat: add output_schema() method to IntoCallToolResult trait - Add output_schema() method with default None implementation - Implement output_schema() for Json<T> to return cached schema - Implement output_schema() for Result<Json<T>, E> delegating to Json<T> - Enable trait-based schema generation for structured outputs * feat: update macro to detect Json<T> wrapper for output schemas - Add extract_json_inner_type() helper to detect Json<T> types - Update schema generation to only occur for Json<T> wrapped types - Remove generic Result<T, E> detection in favor of specific Json<T> detection - Add comprehensive tests to verify schema generation behavior * feat: add builder methods to Tool struct for setting schemas - Add with_output_schema<T>() method to set output schema from type - Add with_input_schema<T>() method to set input schema from type - Both methods use cached_schema_for_type internally - Add comprehensive tests for builder methods * fix: address clippy warnings - Add Default implementation for StructuredOutputServer - Fix collapsible else-if in simple-chat-client - No functional changes * style: apply cargo fmt Apply automatic formatting changes to: - examples/simple-chat-client/src/chat.rs - fix line wrapping - crates/rmcp-macros/src/tool.rs - format method chaining - examples/servers/src/structured_output.rs - reorder imports and format function signatures * chore: fix formatting * chore: fix rustdoc redundant link warning * refactor: validate_against_schema * feat: enforce structured_content usage when output_schema is defined This commit implements strict validation to ensure tools with output_schema consistently use structured_content for both success and error responses. Changes: - Enhanced ToolRouter::call() validation to require structured_content when output_schema is present - Added validation that tools with output_schema cannot use regular content field - Added comprehensive tests covering the new strict validation behavior - Created example demonstrating proper structured output usage - Updated TODO.md to track validation improvements This ensures consistent response format and better type safety for MCP clients. * chore: remove TODO.md * refactor: simplify output schema extraction logic in tool macro - Extract complex nested logic into dedicated helper function - Replace deeply nested if-else chains with functional approach - Use early returns and ? operator for cleaner code flow - Reduce 46 lines to 7 lines in main logic while improving readability * chore: run cargo fmt * fix: enforce structured_content usage when output_schema is defined Structured content is returned as a JSON object in the structuredContent field of a result.For backwards compatibility, a tool that returns structured content SHOULD also return the serialized JSON in a TextContent block. https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content Tools may also provide an output schema for validation of structured results. If an output schema is provided: - Servers MUST provide structured results that conform to this schema. - Clients SHOULD validate structured results against this schema. https://modelcontextprotocol.io/specification/2025-06-18/server/tools#output-schema * chore: cargo fmt
This commit is contained in:
Jean-Marc Le Roux
GitHub
parent
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commit
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1 changed files with 2658 additions and 41 deletions
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@ -1181,32 +1181,126 @@ pub type RootsListChangedNotification = NotificationNoParam<RootsListChangedNoti
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///
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/// Contains the content returned by the tool execution and an optional
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/// flag indicating whether the operation resulted in an error.
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#[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
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///
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/// Note: `content` and `structured_content` are mutually exclusive - exactly one must be provided.
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#[derive(Debug, Serialize, 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 CallToolResult {
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/// The content returned by the tool (text, images, etc.)
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pub content: Vec<Content>,
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#[serde(skip_serializing_if = "Option::is_none")]
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pub content: Option<Vec<Content>>,
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/// An optional JSON object that represents the structured result of the tool call
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#[serde(skip_serializing_if = "Option::is_none")]
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pub structured_content: Option<Value>,
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/// Whether this result represents an error condition
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#[serde(skip_serializing_if = "Option::is_none")]
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pub is_error: Option<bool>,
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}
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impl CallToolResult {
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/// Create a successful tool result
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/// Create a successful tool result with unstructured content
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pub fn success(content: Vec<Content>) -> Self {
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CallToolResult {
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content,
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content: Some(content),
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structured_content: None,
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is_error: Some(false),
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}
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}
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/// Create an error tool result
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/// Create an error tool result with unstructured content
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pub fn error(content: Vec<Content>) -> Self {
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CallToolResult {
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content,
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content: Some(content),
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structured_content: None,
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is_error: Some(true),
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}
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}
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/// Create a successful tool result with structured content
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///
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/// # Example
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///
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/// ```rust,ignore
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/// use rmcp::model::CallToolResult;
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/// use serde_json::json;
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///
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/// let result = CallToolResult::structured(json!({
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/// "temperature": 22.5,
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/// "humidity": 65,
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/// "description": "Partly cloudy"
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/// }));
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/// ```
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pub fn structured(value: Value) -> Self {
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CallToolResult {
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content: None,
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structured_content: Some(value),
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is_error: Some(false),
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}
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}
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/// Create an error tool result with structured content
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///
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/// # Example
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///
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/// ```rust,ignore
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/// use rmcp::model::CallToolResult;
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/// use serde_json::json;
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///
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/// let result = CallToolResult::structured_error(json!({
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/// "error_code": "INVALID_INPUT",
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/// "message": "Temperature value out of range",
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/// "details": {
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/// "min": -50,
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/// "max": 50,
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/// "provided": 100
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/// }
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/// }));
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/// ```
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pub fn structured_error(value: Value) -> Self {
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CallToolResult {
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content: None,
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structured_content: Some(value),
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is_error: Some(true),
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}
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}
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/// Validate that content and structured_content are mutually exclusive
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pub fn validate(&self) -> Result<(), &'static str> {
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match (&self.content, &self.structured_content) {
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(Some(_), Some(_)) => Err("content and structured_content are mutually exclusive"),
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(None, None) => Err("either content or structured_content must be provided"),
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_ => Ok(()),
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}
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}
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}
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// Custom deserialize implementation to validate mutual exclusivity
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impl<'de> Deserialize<'de> for CallToolResult {
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fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
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where
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D: serde::Deserializer<'de>,
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{
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#[derive(Deserialize)]
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#[serde(rename_all = "camelCase")]
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struct CallToolResultHelper {
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#[serde(skip_serializing_if = "Option::is_none")]
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content: Option<Vec<Content>>,
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#[serde(skip_serializing_if = "Option::is_none")]
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structured_content: Option<Value>,
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#[serde(skip_serializing_if = "Option::is_none")]
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is_error: Option<bool>,
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}
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let helper = CallToolResultHelper::deserialize(deserializer)?;
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let result = CallToolResult {
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content: helper.content,
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structured_content: helper.structured_content,
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is_error: helper.is_error,
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};
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// Validate mutual exclusivity
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result.validate().map_err(serde::de::Error::custom)?;
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Ok(result)
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}
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}
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const_string!(ListToolsRequestMethod = "tools/list");
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