docs: condense SEP-2260 rustdoc sections

Tightens the duplicated per-method association section from eleven lines
to five, and trims the marker and SessionManager docs to the same
information in fewer words.

Author: gocamille

crates/rmcp/src/service.rs

@@ -176,20 +176,13 @@ pub(crate) fn in_request_handler_scope() -> bool {
     ORIGINATING_REQUEST.try_with(|_| ()).is_ok()
 }
 
-/// Marker stored in an outbound request's [`Extensions`]
-/// identifying the in-flight peer request it was issued from (SEP-2260).
-///
-/// Attached automatically whenever a request is sent from within a request
-/// handler, for both roles; currently only the streamable HTTP server reads
-/// it, to deliver server-initiated requests on the originating client
-/// request's SSE stream.
-///
-/// # In-memory only
-///
-/// `Extensions` are never serialized, so this marker does not appear on the
-/// wire (SEP-2260 defines no wire field). Session managers that serialize
-/// messages between processes lose it; such requests fall back to the
-/// standalone stream (logged as a warning).
+/// Marker in an outbound request's non-serialized [`Extensions`] identifying
+/// the in-flight peer request it was issued from (SEP-2260). Attached for both
+/// roles whenever a request is sent from within a request handler; the
+/// streamable HTTP server reads it to deliver server-initiated requests on the
+/// originating request's SSE stream. Never on the wire (SEP-2260 defines no
+/// wire field), so session managers that serialize messages between processes
+/// lose it and such requests fall back to the standalone stream with a warning.
 #[derive(Debug, Clone, PartialEq, Eq)]
 #[expect(clippy::exhaustive_structs, reason = "intentionally exhaustive")]
 pub struct OriginatingRequestId(pub RequestId);

crates/rmcp/src/service/server.rs

@@ -771,15 +771,10 @@ impl Peer<RoleServer> {
 
     /// # SEP-2260: request association
     ///
-    /// From protocol version `2026-07-28`, this request must be issued while
-    /// handling a client request — call it on the [`Peer`] from a
-    /// [`RequestContext`], from the handler's
-    /// own task. Calling it outside a handler returns an
-    /// `invalid_request` error. Note that task-local association does not
-    /// cross `tokio::spawn`: a task spawned inside a handler is treated as
-    /// outside the handler — use the task manager for long-running work.
-    /// Requests issued in-handler are delivered on the originating request's
-    /// SSE stream in the streamable HTTP transport.
+    /// From protocol version `2026-07-28` this must be issued while handling a
+    /// client request; outside a handler it returns an `invalid_request` error.
+    /// The association does not cross `tokio::spawn`, so use the task manager
+    /// for long-running work.
     #[deprecated(
         since = "1.8.0",
         note = "Sampling is deprecated by SEP-2577 and will be removed in a future release. See https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2577"
@@ -816,15 +811,10 @@ impl Peer<RoleServer> {
     method!(
         /// # SEP-2260: request association
         ///
-        /// From protocol version `2026-07-28`, this request must be issued while
-        /// handling a client request — call it on the [`Peer`] from a
-        /// [`RequestContext`], from the handler's
-        /// own task. Calling it outside a handler returns an
-        /// `invalid_request` error. Note that task-local association does not
-        /// cross `tokio::spawn`: a task spawned inside a handler is treated as
-        /// outside the handler — use the task manager for long-running work.
-        /// Requests issued in-handler are delivered on the originating request's
-        /// SSE stream in the streamable HTTP transport.
+        /// From protocol version `2026-07-28` this must be issued while handling a
+        /// client request; outside a handler it returns an `invalid_request` error.
+        /// The association does not cross `tokio::spawn`, so use the task manager
+        /// for long-running work.
         #[deprecated(
             since = "1.8.0",
             note = "Roots is deprecated by SEP-2577 and will be removed in a future release. See https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2577"
@@ -835,30 +825,20 @@ impl Peer<RoleServer> {
     method!(
         /// # SEP-2260: request association
         ///
-        /// From protocol version `2026-07-28`, this request must be issued while
-        /// handling a client request — call it on the [`Peer`] from a
-        /// [`RequestContext`], from the handler's
-        /// own task. Calling it outside a handler returns an
-        /// `invalid_request` error. Note that task-local association does not
-        /// cross `tokio::spawn`: a task spawned inside a handler is treated as
-        /// outside the handler — use the task manager for long-running work.
-        /// Requests issued in-handler are delivered on the originating request's
-        /// SSE stream in the streamable HTTP transport.
+        /// From protocol version `2026-07-28` this must be issued while handling a
+        /// client request; outside a handler it returns an `invalid_request` error.
+        /// The association does not cross `tokio::spawn`, so use the task manager
+        /// for long-running work.
         peer_req create_elicitation ElicitRequest(ElicitRequestParams) => ElicitResult
     );
     #[cfg(feature = "elicitation")]
     method!(
         /// # SEP-2260: request association
         ///
-        /// From protocol version `2026-07-28`, this request must be issued while
-        /// handling a client request — call it on the [`Peer`] from a
-        /// [`RequestContext`], from the handler's
-        /// own task. Calling it outside a handler returns an
-        /// `invalid_request` error. Note that task-local association does not
-        /// cross `tokio::spawn`: a task spawned inside a handler is treated as
-        /// outside the handler — use the task manager for long-running work.
-        /// Requests issued in-handler are delivered on the originating request's
-        /// SSE stream in the streamable HTTP transport.
+        /// From protocol version `2026-07-28` this must be issued while handling a
+        /// client request; outside a handler it returns an `invalid_request` error.
+        /// The association does not cross `tokio::spawn`, so use the task manager
+        /// for long-running work.
         peer_req_with_timeout create_elicitation_with_timeout ElicitRequest(ElicitRequestParams) => ElicitResult
     );
 
@@ -1090,15 +1070,10 @@ impl Peer<RoleServer> {
     ///
     /// # SEP-2260: request association
     ///
-    /// From protocol version `2026-07-28`, this request must be issued while
-    /// handling a client request — call it on the [`Peer`] from a
-    /// [`RequestContext`], from the handler's
-    /// own task. Calling it outside a handler returns an
-    /// `invalid_request` error. Note that task-local association does not
-    /// cross `tokio::spawn`: a task spawned inside a handler is treated as
-    /// outside the handler — use the task manager for long-running work.
-    /// Requests issued in-handler are delivered on the originating request's
-    /// SSE stream in the streamable HTTP transport.
+    /// From protocol version `2026-07-28` this must be issued while handling a
+    /// client request; outside a handler it returns an `invalid_request` error.
+    /// The association does not cross `tokio::spawn`, so use the task manager
+    /// for long-running work.
     #[cfg(all(feature = "schemars", feature = "elicitation"))]
     pub async fn elicit<T>(&self, message: impl Into<String>) -> Result<Option<T>, ElicitationError>
     where
@@ -1163,15 +1138,10 @@ impl Peer<RoleServer> {
     ///
     /// # SEP-2260: request association
     ///
-    /// From protocol version `2026-07-28`, this request must be issued while
-    /// handling a client request — call it on the [`Peer`] from a
-    /// [`RequestContext`], from the handler's
-    /// own task. Calling it outside a handler returns an
-    /// `invalid_request` error. Note that task-local association does not
-    /// cross `tokio::spawn`: a task spawned inside a handler is treated as
-    /// outside the handler — use the task manager for long-running work.
-    /// Requests issued in-handler are delivered on the originating request's
-    /// SSE stream in the streamable HTTP transport.
+    /// From protocol version `2026-07-28` this must be issued while handling a
+    /// client request; outside a handler it returns an `invalid_request` error.
+    /// The association does not cross `tokio::spawn`, so use the task manager
+    /// for long-running work.
     #[cfg(all(feature = "schemars", feature = "elicitation"))]
     pub async fn elicit_with_timeout<T>(
         &self,
@@ -1270,15 +1240,10 @@ impl Peer<RoleServer> {
     ///
     /// # SEP-2260: request association
     ///
-    /// From protocol version `2026-07-28`, this request must be issued while
-    /// handling a client request — call it on the [`Peer`] from a
-    /// [`RequestContext`], from the handler's
-    /// own task. Calling it outside a handler returns an
-    /// `invalid_request` error. Note that task-local association does not
-    /// cross `tokio::spawn`: a task spawned inside a handler is treated as
-    /// outside the handler — use the task manager for long-running work.
-    /// Requests issued in-handler are delivered on the originating request's
-    /// SSE stream in the streamable HTTP transport.
+    /// From protocol version `2026-07-28` this must be issued while handling a
+    /// client request; outside a handler it returns an `invalid_request` error.
+    /// The association does not cross `tokio::spawn`, so use the task manager
+    /// for long-running work.
     #[cfg(feature = "elicitation")]
     pub async fn elicit_url(
         &self,
@@ -1333,15 +1298,10 @@ impl Peer<RoleServer> {
     ///
     /// # SEP-2260: request association
     ///
-    /// From protocol version `2026-07-28`, this request must be issued while
-    /// handling a client request — call it on the [`Peer`] from a
-    /// [`RequestContext`], from the handler's
-    /// own task. Calling it outside a handler returns an
-    /// `invalid_request` error. Note that task-local association does not
-    /// cross `tokio::spawn`: a task spawned inside a handler is treated as
-    /// outside the handler — use the task manager for long-running work.
-    /// Requests issued in-handler are delivered on the originating request's
-    /// SSE stream in the streamable HTTP transport.
+    /// From protocol version `2026-07-28` this must be issued while handling a
+    /// client request; outside a handler it returns an `invalid_request` error.
+    /// The association does not cross `tokio::spawn`, so use the task manager
+    /// for long-running work.
     #[cfg(feature = "elicitation")]
     pub async fn elicit_url_with_timeout(
         &self,

crates/rmcp/src/transport/streamable_http_server/session.rs

@@ -77,13 +77,11 @@ pub enum RestoreOutcome<T> {
 ///
 /// Server-initiated requests issued while handling a client request carry an
 /// [`OriginatingRequestId`](crate::service::OriginatingRequestId) marker in
-/// their non-serialized `Extensions`. Implementations that keep messages
-/// in-memory (like the bundled local session manager) deliver such requests on
-/// the originating request's SSE stream, per SEP-2260. Implementations that
-/// serialize messages between processes lose the marker; those requests then
-/// fall back to the standalone stream, which violates SEP-2260 for protocol
-/// version 2026-07-28+ clients — distributed session managers need their own
-/// association mechanism.
+/// their non-serialized `Extensions`; the bundled local session manager uses
+/// it to deliver such requests on the originating request's SSE stream.
+/// Implementations that serialize messages between processes lose the marker
+/// and fall back to the standalone stream, violating SEP-2260 for 2026-07-28+
+/// clients; they need their own association mechanism.
 pub trait SessionManager: Send + Sync + 'static {
     type Error: std::error::Error + Send + 'static;
     type Transport: crate::transport::Transport<RoleServer>;