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feat!: add server discovery and negotiation (SEP-2575) (#973)

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* feat!: add server discovery and negotiation

* feat!: make protocol unions extensible

* ci: add discovery conformance coverage
This commit is contained in:
Dale Seo 2026-07-16 13:47:30 -04:00 • committed by GitHub
commit 3549e86d28
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1 changed files with 1325 additions and 98 deletions
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51
crates/rmcp/src/service/client.rs
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@ -10,17 +10,19 @@ use crate::{
ArgumentInfo, CallToolRequest, CallToolRequestParams, CallToolResponse, CallToolResult,
CancelledNotification, CancelledNotificationParam, ClientInfo, ClientJsonRpcMessage,
ClientNotification, ClientRequest, ClientResult, CompleteRequest, CompleteRequestParams,
CompleteResult, CompletionContext, CompletionInfo, DEFAULT_MRTR_MAX_ROUNDS, ErrorData,
GetExtensions, GetMeta, GetPromptRequest, GetPromptRequestParams, GetPromptResponse,
GetPromptResult, InitializeRequest, InitializedNotification, InputRequest,
InputRequiredResult, InputResponses, JsonRpcResponse, ListPromptsRequest,
ListPromptsResult, ListResourceTemplatesRequest, ListResourceTemplatesResult,
ListResourcesRequest, ListResourcesResult, ListToolsRequest, ListToolsResult,
NumberOrString, PaginatedRequestParams, ProgressNotification, ProgressNotificationParam,
CompleteResult, CompletionContext, CompletionInfo, DEFAULT_MRTR_MAX_ROUNDS,
DiscoverRequest, DiscoverRequestParams, DiscoverResult, ErrorData, GetExtensions, GetMeta,
GetPromptRequest, GetPromptRequestParams, GetPromptResponse, GetPromptResult,
InitializeRequest, InitializedNotification, InputRequest, InputRequiredResult,
InputResponses, JsonRpcResponse, ListPromptsRequest, ListPromptsResult,
ListResourceTemplatesRequest, ListResourceTemplatesResult, ListResourcesRequest,
ListResourcesResult, ListToolsRequest, ListToolsResult, NumberOrString,
PaginatedRequestParams, ProgressNotification, ProgressNotificationParam, ProtocolVersion,
ReadResourceRequest, ReadResourceRequestParams, ReadResourceResponse, ReadResourceResult,
Reference, RequestId, RootsListChangedNotification, ServerInfo, ServerJsonRpcMessage,
ServerNotification, ServerRequest, ServerResult, SetLevelRequest, SetLevelRequestParams,
SubscribeRequest, SubscribeRequestParams, UnsubscribeRequest, UnsubscribeRequestParams,
Reference, RequestId, RequestMetaObject, RootsListChangedNotification, ServerInfo,
ServerJsonRpcMessage, ServerNotification, ServerRequest, ServerResult, SetLevelRequest,
SetLevelRequestParams, SubscribeRequest, SubscribeRequestParams, UnsubscribeRequest,
UnsubscribeRequestParams,
},
transport::DynamicTransportError,
};
@ -147,6 +149,19 @@ where
#[expect(clippy::exhaustive_structs, reason = "intentionally exhaustive")]
pub struct RoleClient;
/// Select the first client-preferred protocol version supported by the server.
///
/// Returns `None` when no version is shared.
pub fn select_protocol_version(
client_preference: &[ProtocolVersion],
server_supported: &[ProtocolVersion],
) -> Option<ProtocolVersion> {
client_preference
.iter()
.find(|version| server_supported.contains(version))
.cloned()
}
impl ServiceRole for RoleClient {
type Req = ClientRequest;
type Resp = ClientResult;
@ -363,6 +378,22 @@ macro_rules! method {
}
impl Peer<RoleClient> {
/// Discover the server's supported protocol versions and capabilities.
///
/// The high-level client currently exposes this peer only after initialization;
/// pre-initialization probing is planned as follow-up work.
pub async fn discover(&self, meta: RequestMetaObject) -> Result<DiscoverResult, ServiceError> {
let mut request = DiscoverRequest::new(DiscoverRequestParams {});
request.extensions.insert(meta);
let result = self
.send_request(ClientRequest::DiscoverRequest(request))
.await?;
match result {
ServerResult::DiscoverResult(result) => Ok(result),
_ => Err(ServiceError::UnexpectedResponse),
}
}
/// Send one `tools/call` request and return either a final result or an MRTR
/// `InputRequiredResult` without driving any follow-up rounds.
pub async fn call_tool_once(