feat: enable tool access to HTTP request headers

crates/rmcp/src/handler/server/tool.rs

@@ -80,6 +80,9 @@ impl<'service, S> ToolCallContext<'service, S> {
     pub fn name(&self) -> &str {
         &self.name
     }
+    pub fn request_context(&self) -> &RequestContext<RoleServer> {
+        &self.request_context
+    }
 }
 
 pub trait FromToolCallContextPart<'a, S>: Sized {

crates/rmcp/src/transport/sse_server.rs

@@ -3,7 +3,7 @@ use std::{collections::HashMap, io, net::SocketAddr, sync::Arc, time::Duration};
 use axum::{
     Json, Router,
     extract::{Query, State},
-    http::{StatusCode, request::Parts},
+    http::{self, StatusCode, request::Parts},
     response::{
         Response,
         sse::{Event, KeepAlive, Sse},
@@ -74,7 +74,8 @@ async fn post_event_handler(
             .ok_or(StatusCode::NOT_FOUND)?
             .clone()
     };
-    message.insert_extension(parts);
+    let headers_to_insert: http::HeaderMap = parts.headers.clone();
+    message.insert_extension(headers_to_insert);
     if tx.send(message).await.is_err() {
         tracing::error!("send message error");
         return Err(StatusCode::GONE);

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

@@ -3,7 +3,7 @@ use std::{collections::HashMap, io, net::SocketAddr, sync::Arc, time::Duration};
 use axum::{
     Json, Router,
     extract::State,
-    http::{HeaderMap, HeaderValue, StatusCode, request::Parts},
+    http::{self, HeaderMap, HeaderValue, StatusCode, request::Parts},
     response::{
         IntoResponse, Response,
         sse::{Event, KeepAlive, Sse},
@@ -84,8 +84,8 @@ async fn post_handler(
                 .ok_or((StatusCode::NOT_FOUND, "session not found").into_response())?;
             session.handle().clone()
         };
-        // inject request part
-        message.insert_extension(parts);
+        let headers_to_insert: http::HeaderMap = parts.headers.clone();
+        message.insert_extension(headers_to_insert);
         match &message {
             ClientJsonRpcMessage::Request(_) | ClientJsonRpcMessage::BatchRequest(_) => {
                 let receiver = handle.establish_request_wise_channel().await.map_err(|e| {

examples/servers/src/common/counter.rs

@@ -1,12 +1,12 @@
 use std::sync::Arc;
 
+use crate::common::extractor::ReqHeaders;
 use rmcp::{
     Error as McpError, RoleServer, ServerHandler, const_string, model::*, schemars,
     service::RequestContext, tool,
 };
 use serde_json::json;
 use tokio::sync::Mutex;
-
 #[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
 pub struct StructRequest {
     pub a: i32,
@@ -81,6 +81,18 @@ impl Counter {
             (a + b).to_string(),
         )]))
     }
+    #[tool(description = "Get the request headers")]
+    fn get_headers(&self, ReqHeaders(headers): ReqHeaders) -> Result<CallToolResult, McpError> {
+        let mut header_strings = Vec::new();
+        for (name, value) in headers.iter() {
+            if let Ok(value_str) = value.to_str() {
+                header_strings.push(format!("{}: {}", name, value_str));
+            }
+        }
+        Ok(CallToolResult::success(vec![Content::text(
+            header_strings.join("\n"),
+        )]))
+    }
 }
 const_string!(Echo = "echo");
 #[tool(tool_box)]

examples/servers/src/common/extractor.rs

@@ -0,0 +1,20 @@
+use axum::http::HeaderMap;
+use rmcp::Error as McpError;
+use rmcp::handler::server::tool::{FromToolCallContextPart, ToolCallContext};
+
+#[derive(Debug)]
+pub struct ReqHeaders(pub HeaderMap);
+
+impl<'a, S> FromToolCallContextPart<'a, S> for ReqHeaders {
+    fn from_tool_call_context_part(
+        context: ToolCallContext<'a, S>,
+    ) -> Result<(Self, ToolCallContext<'a, S>), McpError> {
+        match context.request_context().extensions.get::<HeaderMap>() {
+            Some(headers) => Ok((ReqHeaders(headers.clone()), context)),
+            None => Err(McpError::internal_error(
+                "HTTP headers not found in context.",
+                None,
+            )),
+        }
+    }
+}

examples/servers/src/common/mod.rs

@@ -1,3 +1,4 @@
 pub mod calculator;
 pub mod counter;
+pub mod extractor;
 pub mod generic_service;