feat(acp): Extract all rmcp logic to the rmcp crate

Cargo.toml

@@ -2,11 +2,11 @@
 members = [
     "src/agent-client-protocol",
     "src/agent-client-protocol-derive",
-    # Keep polyfill before conductor: release-plz currently ignores versioned
+    # Keep polyfill and rmcp before conductor: release-plz currently ignores versioned
     # dev-dependency edges, but cargo publish still validates them.
     "src/agent-client-protocol-polyfill",
-    "src/agent-client-protocol-conductor",
     "src/agent-client-protocol-rmcp",
+    "src/agent-client-protocol-conductor",
     "src/agent-client-protocol-test",
     "src/agent-client-protocol-trace-viewer",
     "src/yopo",

md/design.md

@@ -14,7 +14,7 @@ The core SDK. Provides:
 - **Connection builders** (`builder()`, `connect_to()`, `connect_with()`)
 - **Message handling** (`on_receive_request`, `on_receive_notification`, `on_receive_dispatch`)
 - **Protocol types** (`agent_client_protocol::schema::*`) - all ACP message types
-- **MCP server builder** - for adding tools to proxies
+- **MCP server attachment** - runtime-agnostic interfaces for wiring MCP servers into ACP sessions
 
 ### agent-client-protocol-tokio
 
@@ -27,6 +27,7 @@ Tokio-specific utilities:
 
 Integration with the [rmcp](https://docs.rs/rmcp) crate:
 
+- **`McpServer::builder()`** - define MCP tools in Rust code
 - **`McpServer::from_rmcp()`** - wrap an rmcp server as an ACP MCP server
 
 ## Role System
@@ -156,7 +157,7 @@ stateDiagram-v2
 | `src/agent-client-protocol/src/component.rs` | ConnectTo and Builder traits          |
 | `src/agent-client-protocol/src/handler.rs`   | Connection builder implementation     |
 | `src/agent-client-protocol/src/typed.rs`     | Dispatch type and handler matching    |
-| `src/agent-client-protocol/src/mcp_server/`  | MCP server builder                    |
+| `src/agent-client-protocol/src/mcp_server/`  | Runtime-agnostic MCP server attachment |
 | `src/agent-client-protocol/src/concepts/`    | Rustdoc concept explanations          |
 
 ## Design Decisions

src/agent-client-protocol-conductor/Cargo.toml

@@ -37,6 +37,7 @@ uuid.workspace = true
 
 [dev-dependencies]
 agent-client-protocol = { workspace = true, features = ["unstable_mcp_over_acp"] }
+agent-client-protocol-rmcp.workspace = true
 agent-client-protocol-test.workspace = true
 yopo.workspace = true
 expect-test.workspace = true

src/agent-client-protocol-conductor/tests/mcp_integration/proxy.rs

@@ -2,6 +2,7 @@
 
 use agent_client_protocol::mcp_server::McpServer;
 use agent_client_protocol::{Conductor, ConnectTo, Proxy};
+use agent_client_protocol_rmcp::McpServerExt as _;
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
 

src/agent-client-protocol-conductor/tests/mcp_server_handler_chain.rs

@@ -12,6 +12,7 @@ use agent_client_protocol::schema::{
 };
 use agent_client_protocol::{Agent, Client, Conductor, ConnectTo, DynConnectTo, Proxy};
 use agent_client_protocol_conductor::{ConductorImpl, ProxiesAndAgent};
+use agent_client_protocol_rmcp::McpServerExt as _;
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
 use std::path::PathBuf;

src/agent-client-protocol-conductor/tests/scoped_mcp_server.rs

@@ -8,6 +8,7 @@ use agent_client_protocol::mcp_server::McpServer;
 use agent_client_protocol::{Agent, Conductor, ConnectTo, Proxy, Role, RunWithConnectionTo};
 use agent_client_protocol_conductor::{ConductorImpl, ProxiesAndAgent};
 use agent_client_protocol_polyfill::mcp_over_acp::McpOverAcpPolyfill;
+use agent_client_protocol_rmcp::McpServerExt as _;
 use agent_client_protocol_test::testy::{Testy, TestyCommand};
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};

src/agent-client-protocol-conductor/tests/standalone_mcp_server.rs

@@ -6,6 +6,7 @@
 use agent_client_protocol::{
     ByteStreams, ConnectTo, RunWithConnectionTo, mcp_server::McpServer, role::mcp, util::run_until,
 };
+use agent_client_protocol_rmcp::McpServerExt as _;
 use rmcp::{ClientHandler, ServiceExt, model::ClientInfo};
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};

src/agent-client-protocol-conductor/tests/test_mcp_tool_output_types.rs

@@ -7,6 +7,7 @@ use agent_client_protocol::mcp_server::McpServer;
 use agent_client_protocol::{Conductor, ConnectTo, DynConnectTo, Proxy, RunWithConnectionTo};
 use agent_client_protocol_conductor::{ConductorImpl, ProxiesAndAgent};
 use agent_client_protocol_polyfill::mcp_over_acp::McpOverAcpPolyfill;
+use agent_client_protocol_rmcp::McpServerExt as _;
 use agent_client_protocol_test::testy::{Testy, TestyCommand};
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};

src/agent-client-protocol-conductor/tests/test_session_id_in_mcp_tools.rs

@@ -13,6 +13,7 @@ use agent_client_protocol::mcp_server::McpServer;
 use agent_client_protocol::{Conductor, ConnectTo, DynConnectTo, Proxy};
 use agent_client_protocol_conductor::{ConductorImpl, ProxiesAndAgent};
 use agent_client_protocol_polyfill::mcp_over_acp::McpOverAcpPolyfill;
+use agent_client_protocol_rmcp::McpServerExt as _;
 use agent_client_protocol_test::testy::{Testy, TestyCommand};
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};

src/agent-client-protocol-conductor/tests/test_tool_enable_disable.rs

@@ -7,6 +7,7 @@ use agent_client_protocol::mcp_server::McpServer;
 use agent_client_protocol::{Conductor, ConnectTo, DynConnectTo, Proxy, RunWithConnectionTo};
 use agent_client_protocol_conductor::{ConductorImpl, ProxiesAndAgent};
 use agent_client_protocol_polyfill::mcp_over_acp::McpOverAcpPolyfill;
+use agent_client_protocol_rmcp::McpServerExt as _;
 use agent_client_protocol_test::testy::{Testy, TestyCommand};
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};

src/agent-client-protocol-conductor/tests/test_tool_fn.rs

@@ -7,6 +7,7 @@ use agent_client_protocol::mcp_server::McpServer;
 use agent_client_protocol::{Conductor, ConnectTo, DynConnectTo, Proxy, RunWithConnectionTo};
 use agent_client_protocol_conductor::{ConductorImpl, ProxiesAndAgent};
 use agent_client_protocol_polyfill::mcp_over_acp::McpOverAcpPolyfill;
+use agent_client_protocol_rmcp::McpServerExt as _;
 use agent_client_protocol_test::testy::{Testy, TestyCommand};
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};

src/agent-client-protocol-conductor/tests/trace_client_mcp_server.rs

@@ -15,6 +15,7 @@ use agent_client_protocol::{Client, Role, RunWithConnectionTo};
 use agent_client_protocol_conductor::trace::TraceEvent;
 use agent_client_protocol_conductor::{ConductorImpl, ProxiesAndAgent};
 use agent_client_protocol_polyfill::mcp_over_acp::McpOverAcpPolyfill;
+use agent_client_protocol_rmcp::McpServerExt as _;
 use agent_client_protocol_test::testy::{Testy, TestyCommand};
 use expect_test::expect;
 use futures::StreamExt;

src/agent-client-protocol-cookbook/src/lib.rs

@@ -455,6 +455,7 @@ pub mod global_mcp_server {
     //!
     //! ```
     //! use agent_client_protocol::mcp_server::McpServer;
+    //! use agent_client_protocol_rmcp::McpServerExt;
     //! use agent_client_protocol::{ConnectTo, RunWithConnectionTo, Proxy, Conductor};
     //! use schemars::JsonSchema;
     //! use serde::{Deserialize, Serialize};
@@ -556,7 +557,7 @@ pub mod global_mcp_server {
     //! 2. Passes the modified request through to the next handler
     //! 3. Handles incoming MCP protocol messages (tool calls, etc.) for its URL
     //!
-    //! [`McpServer::builder`]: agent_client_protocol::mcp_server::McpServer::builder
+    //! [`McpServer::builder`]: agent_client_protocol_rmcp::McpServerExt::builder
     //! [`McpServer::from_rmcp`]: agent_client_protocol_rmcp::McpServerExt::from_rmcp
     //! [`with_mcp_server`]: agent_client_protocol::Builder::with_mcp_server
 }
@@ -581,6 +582,7 @@ pub mod per_session_mcp_server {
     //!
     //! ```
     //! use agent_client_protocol::mcp_server::McpServer;
+    //! use agent_client_protocol_rmcp::McpServerExt;
     //! use agent_client_protocol::schema::NewSessionRequest;
     //! use agent_client_protocol::{Client, Proxy, Conductor, ConnectTo};
     //!
@@ -639,6 +641,7 @@ pub mod per_session_mcp_server {
     //!
     //! ```
     //! # use agent_client_protocol::mcp_server::McpServer;
+    //! # use agent_client_protocol_rmcp::McpServerExt;
     //! # use agent_client_protocol::schema::NewSessionRequest;
     //! # use agent_client_protocol::{Client, Proxy, Conductor, ConnectTo};
     //! # async fn run_proxy(transport: impl ConnectTo<Proxy>) -> Result<(), agent_client_protocol::Error> {
@@ -694,6 +697,7 @@ pub mod filtering_tools {
     //!
     //! ```
     //! use agent_client_protocol::mcp_server::McpServer;
+    //! use agent_client_protocol_rmcp::McpServerExt;
     //! use agent_client_protocol::{Conductor, RunWithConnectionTo};
     //! use schemars::JsonSchema;
     //! use serde::Deserialize;
@@ -730,6 +734,7 @@ pub mod filtering_tools {
     //!
     //! ```
     //! use agent_client_protocol::mcp_server::McpServer;
+    //! use agent_client_protocol_rmcp::McpServerExt;
     //! use agent_client_protocol::{Conductor, RunWithConnectionTo};
     //! use schemars::JsonSchema;
     //! use serde::Deserialize;
@@ -763,6 +768,7 @@ pub mod filtering_tools {
     //!
     //! ```
     //! use agent_client_protocol::mcp_server::McpServer;
+    //! use agent_client_protocol_rmcp::McpServerExt;
     //! use agent_client_protocol::Conductor;
     //!
     //! // This will error because "ech" is not a registered tool
@@ -775,9 +781,9 @@ pub mod filtering_tools {
     //! Calling enable/disable on an already enabled/disabled tool is not an error -
     //! the operations are idempotent.
     //!
-    //! [`disable_tool`]: agent_client_protocol::mcp_server::McpServerBuilder::disable_tool
-    //! [`enable_tool`]: agent_client_protocol::mcp_server::McpServerBuilder::enable_tool
-    //! [`disable_all_tools`]: agent_client_protocol::mcp_server::McpServerBuilder::disable_all_tools
+    //! [`disable_tool`]: agent_client_protocol_rmcp::McpServerBuilder::disable_tool
+    //! [`enable_tool`]: agent_client_protocol_rmcp::McpServerBuilder::enable_tool
+    //! [`disable_all_tools`]: agent_client_protocol_rmcp::McpServerBuilder::disable_all_tools
 }
 
 pub mod running_proxies_with_conductor {

src/agent-client-protocol-rmcp/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Add the MCP server builder APIs moved out of `agent-client-protocol`, keeping `rmcp` and Tokio dependencies in this integration crate.
+
 ## [0.11.2](https://github.com/agentclientprotocol/rust-sdk/compare/agent-client-protocol-rmcp-v0.11.1...agent-client-protocol-rmcp-v0.11.2) - 2026-05-16
 
 ### Other

src/agent-client-protocol-rmcp/Cargo.toml

@@ -12,14 +12,16 @@ categories = ["development-tools"]
 
 [dependencies]
 agent-client-protocol.workspace = true
+futures.workspace = true
 futures-concurrency.workspace = true
 rmcp.workspace = true
+schemars.workspace = true
+serde.workspace = true
+serde_json.workspace = true
 tokio.workspace = true
 tokio-util.workspace = true
 
 [dev-dependencies]
-schemars.workspace = true
-serde.workspace = true
 tracing.workspace = true
 tracing-subscriber.workspace = true
 

src/agent-client-protocol-rmcp/README.md

@@ -4,11 +4,20 @@
 
 ## Overview
 
-This crate bridges [rmcp](https://docs.rs/rmcp)-based MCP server implementations with the ACP MCP server framework from `agent-client-protocol`. It lets you use any rmcp service as an MCP server in an ACP proxy.
+This crate bridges [rmcp](https://docs.rs/rmcp)-based MCP server implementations with the ACP MCP server framework from `agent-client-protocol`. It lets you define MCP tools in Rust or use any rmcp service as an MCP server in an ACP proxy.
 
 ## Usage
 
-Use the `McpServerExt` trait to create an MCP server from an rmcp service:
+Use the `McpServerExt` trait to build an MCP server with tools:
+
+```rust
+use agent_client_protocol::mcp_server::McpServer;
+use agent_client_protocol_rmcp::McpServerExt;
+
+let server = McpServer::builder("my-tools").build();
+```
+
+Or create an MCP server from an rmcp service:
 
 ```rust
 use agent_client_protocol::mcp_server::McpServer;