feat(unstable): make MCP-over-ACP request-scoped

agent-client-protocol-schema/src/serde_util.rs

@@ -135,10 +135,6 @@ mod default_on_null_tests {
                 $check::<v1::StartNesRequest>();
                 $check::<v1::CloseNesResponse>();
             }
-            #[cfg(feature = "unstable_mcp_over_acp")]
-            {
-                $check::<v1::DisconnectMcpResponse>();
-            }
 
             #[cfg(feature = "unstable_protocol_v2")]
             {
@@ -163,10 +159,6 @@ mod default_on_null_tests {
                     $check::<v2::StartNesRequest>();
                     $check::<v2::CloseNesResponse>();
                 }
-                #[cfg(feature = "unstable_mcp_over_acp")]
-                {
-                    $check::<v2::DisconnectMcpResponse>();
-                }
             }
         };
     }
@@ -355,8 +347,9 @@ mod default_on_null_tests {
 
         #[cfg(feature = "unstable_mcp_over_acp")]
         {
-            let mcp: v1::MessageMcpResponse = serde_json::from_value(Value::Null).unwrap();
-            assert_eq!(serde_json::to_value(mcp).unwrap(), Value::Null);
+            let mcp: v1::MessageMcpResponse =
+                serde_json::from_value(json!({"result": null})).unwrap();
+            assert_eq!(serde_json::to_value(mcp).unwrap(), json!({"result": null}));
         }
 
         #[cfg(feature = "unstable_protocol_v2")]
@@ -367,8 +360,8 @@ mod default_on_null_tests {
             #[cfg(feature = "unstable_mcp_over_acp")]
             {
                 let mcp: crate::v2::MessageMcpResponse =
-                    serde_json::from_value(Value::Null).unwrap();
-                assert_eq!(serde_json::to_value(mcp).unwrap(), Value::Null);
+                    serde_json::from_value(json!({"result": null})).unwrap();
+                assert_eq!(serde_json::to_value(mcp).unwrap(), json!({"result": null}));
             }
         }
     }

agent-client-protocol-schema/src/v1/agent.rs

@@ -18,9 +18,7 @@ use super::{
 };
 
 #[cfg(feature = "unstable_mcp_over_acp")]
-use super::mcp::{
-    MCP_MESSAGE_METHOD_NAME, MessageMcpNotification, MessageMcpRequest, MessageMcpResponse,
-};
+use super::mcp::{MCP_MESSAGE_METHOD_NAME, MessageMcpNotification};
 
 #[cfg(feature = "unstable_nes")]
 use super::{
@@ -2796,8 +2794,7 @@ impl McpServerSse {
 /// Unique identifier for an MCP server using the ACP transport.
 ///
 /// The value is opaque and generated by the ACP component providing the MCP server. It is
-/// used by `mcp/connect` to route connection requests back to the component that declared the
-/// server.
+/// used by `mcp/message` to route requests to the component that declared the server.
 #[cfg(feature = "unstable_mcp_over_acp")]
 #[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, Hash, Display, From)]
@@ -2822,7 +2819,7 @@ impl McpServerAcpId {
 /// ACP transport configuration for MCP.
 ///
 /// The MCP server is provided by an ACP component and communicates over the ACP channel
-/// using `mcp/connect`, `mcp/message`, and `mcp/disconnect`.
+/// using `mcp/message`.
 #[serde_as]
 #[skip_serializing_none]
 #[cfg(feature = "unstable_mcp_over_acp")]
@@ -4962,13 +4959,6 @@ pub enum ClientRequest {
     /// The agent must cancel any ongoing work and then free up any resources
     /// associated with the NES session.
     CloseNesRequest(CloseNesRequest),
-    /// **UNSTABLE**
-    ///
-    /// This capability is not part of the spec yet, and may be removed or changed at any point.
-    ///
-    /// Exchanges an MCP-over-ACP message.
-    #[cfg(feature = "unstable_mcp_over_acp")]
-    MessageMcpRequest(MessageMcpRequest),
     /// Handles extension method requests from the client.
     ///
     /// Extension methods provide a way to add custom functionality while maintaining
@@ -5009,8 +4999,6 @@ impl ClientRequest {
             Self::SuggestNesRequest(_) => AGENT_METHOD_NAMES.nes_suggest,
             #[cfg(feature = "unstable_nes")]
             Self::CloseNesRequest(_) => AGENT_METHOD_NAMES.nes_close,
-            #[cfg(feature = "unstable_mcp_over_acp")]
-            Self::MessageMcpRequest(_) => AGENT_METHOD_NAMES.mcp_message,
             Self::ExtMethodRequest(ext_request) => &ext_request.method,
         }
     }
@@ -5076,9 +5064,6 @@ pub enum AgentResponse {
     CloseNesResponse(#[serde(default)] CloseNesResponse),
     /// Successful result returned by an extension method outside the core ACP method set.
     ExtMethodResponse(ExtResponse),
-    /// Successful result returned by an MCP-over-ACP `mcp/message` request.
-    #[cfg(feature = "unstable_mcp_over_acp")]
-    MessageMcpResponse(MessageMcpResponse),
 }
 
 /// All possible notifications that a client can send to an agent.
@@ -5420,21 +5405,36 @@ mod test_serialization {
     #[cfg(feature = "unstable_mcp_over_acp")]
     #[test]
     fn test_client_mcp_message_method_names() {
+        use serde_json::json;
+
         assert_eq!(AGENT_METHOD_NAMES.mcp_message, "mcp/message");
 
+        let notification =
+            MessageMcpNotification::new("server-1", "req-1", "notifications/progress");
         assert_eq!(
-            ClientRequest::MessageMcpRequest(MessageMcpRequest::new("conn-1", "tools/list"))
-                .method(),
+            ClientNotification::MessageMcpNotification(notification.clone()).method(),
             "mcp/message"
         );
         assert_eq!(
-            ClientNotification::MessageMcpNotification(MessageMcpNotification::new(
-                "conn-1",
-                "notifications/progress"
-            ))
-            .method(),
-            "mcp/message"
+            serde_json::to_value(notification).unwrap(),
+            json!({
+                "serverId": "server-1",
+                "requestId": "req-1",
+                "method": "notifications/progress"
+            })
         );
+        let notification: MessageMcpNotification = serde_json::from_value(json!({
+            "serverId": "server-1", "requestId": "req-1", "method": "notifications/progress",
+            "params": null, "_meta": null
+        }))
+        .unwrap();
+        assert_eq!(notification.params, None);
+        assert_eq!(notification.meta, None);
+        for key in ["serverId", "requestId", "method"] {
+            let mut value = json!({"serverId":"server-1", "requestId":"req-1", "method":"notifications/progress"});
+            value.as_object_mut().unwrap().remove(key);
+            assert!(serde_json::from_value::<MessageMcpNotification>(value).is_err());
+        }
     }
 
     #[cfg(all(feature = "unstable_mcp_over_acp", feature = "schemars"))]

agent-client-protocol-schema/src/v1/client.rs

@@ -23,11 +23,7 @@ use super::{
 use super::{PlanCapabilities, PlanRemoved, PlanUpdate};
 
 #[cfg(feature = "unstable_mcp_over_acp")]
-use super::mcp::{
-    ConnectMcpRequest, ConnectMcpResponse, DisconnectMcpRequest, DisconnectMcpResponse,
-    MCP_CONNECT_METHOD_NAME, MCP_DISCONNECT_METHOD_NAME, MCP_MESSAGE_METHOD_NAME,
-    MessageMcpNotification, MessageMcpRequest, MessageMcpResponse,
-};
+use super::mcp::{MCP_MESSAGE_METHOD_NAME, MessageMcpRequest, MessageMcpResponse};
 
 #[cfg(feature = "unstable_nes")]
 use super::{ClientNesCapabilities, PositionEncodingKind};
@@ -2649,15 +2645,9 @@ pub struct ClientMethodNames {
     pub terminal_wait_for_exit: &'static str,
     /// Method for killing a terminal.
     pub terminal_kill: &'static str,
-    /// Method for opening an MCP-over-ACP connection.
-    #[cfg(feature = "unstable_mcp_over_acp")]
-    pub mcp_connect: &'static str,
     /// Method for exchanging MCP-over-ACP messages.
     #[cfg(feature = "unstable_mcp_over_acp")]
     pub mcp_message: &'static str,
-    /// Method for closing an MCP-over-ACP connection.
-    #[cfg(feature = "unstable_mcp_over_acp")]
-    pub mcp_disconnect: &'static str,
     /// Method for elicitation.
     pub elicitation_create: &'static str,
     /// Notification for elicitation completion.
@@ -2676,11 +2666,7 @@ pub const CLIENT_METHOD_NAMES: ClientMethodNames = ClientMethodNames {
     terminal_wait_for_exit: TERMINAL_WAIT_FOR_EXIT_METHOD_NAME,
     terminal_kill: TERMINAL_KILL_METHOD_NAME,
     #[cfg(feature = "unstable_mcp_over_acp")]
-    mcp_connect: MCP_CONNECT_METHOD_NAME,
-    #[cfg(feature = "unstable_mcp_over_acp")]
     mcp_message: MCP_MESSAGE_METHOD_NAME,
-    #[cfg(feature = "unstable_mcp_over_acp")]
-    mcp_disconnect: MCP_DISCONNECT_METHOD_NAME,
     elicitation_create: ELICITATION_CREATE_METHOD_NAME,
     elicitation_complete: ELICITATION_COMPLETE_NOTIFICATION,
 };
@@ -2806,23 +2792,9 @@ pub enum AgentRequest {
     ///
     /// This capability is not part of the spec yet, and may be removed or changed at any point.
     ///
-    /// Opens an MCP-over-ACP connection.
-    #[cfg(feature = "unstable_mcp_over_acp")]
-    ConnectMcpRequest(ConnectMcpRequest),
-    /// **UNSTABLE**
-    ///
-    /// This capability is not part of the spec yet, and may be removed or changed at any point.
-    ///
     /// Exchanges an MCP-over-ACP message.
     #[cfg(feature = "unstable_mcp_over_acp")]
     MessageMcpRequest(MessageMcpRequest),
-    /// **UNSTABLE**
-    ///
-    /// This capability is not part of the spec yet, and may be removed or changed at any point.
-    ///
-    /// Closes an MCP-over-ACP connection.
-    #[cfg(feature = "unstable_mcp_over_acp")]
-    DisconnectMcpRequest(DisconnectMcpRequest),
     /// Handles extension method requests from the agent.
     ///
     /// Allows the Agent to send an arbitrary request that is not part of the ACP spec.
@@ -2848,11 +2820,7 @@ impl AgentRequest {
             Self::KillTerminalRequest(_) => CLIENT_METHOD_NAMES.terminal_kill,
             Self::CreateElicitationRequest(_) => CLIENT_METHOD_NAMES.elicitation_create,
             #[cfg(feature = "unstable_mcp_over_acp")]
-            Self::ConnectMcpRequest(_) => CLIENT_METHOD_NAMES.mcp_connect,
-            #[cfg(feature = "unstable_mcp_over_acp")]
             Self::MessageMcpRequest(_) => CLIENT_METHOD_NAMES.mcp_message,
-            #[cfg(feature = "unstable_mcp_over_acp")]
-            Self::DisconnectMcpRequest(_) => CLIENT_METHOD_NAMES.mcp_disconnect,
             Self::ExtMethodRequest(ext_request) => &ext_request.method,
         }
     }
@@ -2888,12 +2856,6 @@ pub enum ClientResponse {
     KillTerminalResponse(#[serde(default)] KillTerminalResponse),
     /// Successful result returned for a `elicitation/create` request.
     CreateElicitationResponse(CreateElicitationResponse),
-    /// Successful result returned for a `mcp/connect` request.
-    #[cfg(feature = "unstable_mcp_over_acp")]
-    ConnectMcpResponse(ConnectMcpResponse),
-    /// Successful result returned for a `mcp/disconnect` request.
-    #[cfg(feature = "unstable_mcp_over_acp")]
-    DisconnectMcpResponse(#[serde(default)] DisconnectMcpResponse),
     /// Successful result returned by an MCP-over-ACP `mcp/message` request.
     #[cfg(feature = "unstable_mcp_over_acp")]
     MessageMcpResponse(MessageMcpResponse),
@@ -2930,13 +2892,6 @@ pub enum AgentNotification {
     ///
     /// See protocol docs: [Elicitation](https://agentclientprotocol.com/protocol/elicitation#url-completion)
     CompleteElicitationNotification(CompleteElicitationNotification),
-    /// **UNSTABLE**
-    ///
-    /// This capability is not part of the spec yet, and may be removed or changed at any point.
-    ///
-    /// Receives an MCP-over-ACP notification.
-    #[cfg(feature = "unstable_mcp_over_acp")]
-    MessageMcpNotification(MessageMcpNotification),
     /// Handles extension notifications from the agent.
     ///
     /// Allows the Agent to send an arbitrary notification that is not part of the ACP spec.
@@ -2954,8 +2909,6 @@ impl AgentNotification {
         match self {
             Self::SessionNotification(_) => CLIENT_METHOD_NAMES.session_update,
             Self::CompleteElicitationNotification(_) => CLIENT_METHOD_NAMES.elicitation_complete,
-            #[cfg(feature = "unstable_mcp_over_acp")]
-            Self::MessageMcpNotification(_) => CLIENT_METHOD_NAMES.mcp_message,
             Self::ExtNotification(ext_notification) => &ext_notification.method,
         }
     }
@@ -3613,72 +3566,51 @@ mod tests {
         let params: serde_json::Map<String, serde_json::Value> =
             [("cursor".to_string(), json!("abc"))].into_iter().collect();
 
-        assert_eq!(CLIENT_METHOD_NAMES.mcp_connect, "mcp/connect");
         assert_eq!(CLIENT_METHOD_NAMES.mcp_message, "mcp/message");
-        assert_eq!(CLIENT_METHOD_NAMES.mcp_disconnect, "mcp/disconnect");
-
         assert_eq!(
-            AgentRequest::ConnectMcpRequest(ConnectMcpRequest::new("server-1")).method(),
-            "mcp/connect"
-        );
-        assert_eq!(
-            AgentRequest::MessageMcpRequest(MessageMcpRequest::new("conn-1", "tools/list"))
-                .method(),
-            "mcp/message"
-        );
-        assert_eq!(
-            AgentRequest::DisconnectMcpRequest(DisconnectMcpRequest::new("conn-1")).method(),
-            "mcp/disconnect"
-        );
-        assert_eq!(
-            AgentNotification::MessageMcpNotification(MessageMcpNotification::new(
-                "conn-1",
-                "notifications/progress"
+            AgentRequest::MessageMcpRequest(MessageMcpRequest::new(
+                "server-1",
+                "req-1",
+                "tools/list"
             ))
             .method(),
             "mcp/message"
         );
-
         assert_eq!(
-            serde_json::to_value(ConnectMcpRequest::new("server-1")).unwrap(),
-            json!({ "serverId": "server-1" })
-        );
-        assert_eq!(
-            serde_json::to_value(ConnectMcpResponse::new("conn-1")).unwrap(),
-            json!({ "connectionId": "conn-1" })
-        );
-        assert_eq!(
-            serde_json::to_value(MessageMcpRequest::new("conn-1", "tools/list").params(params))
-                .unwrap(),
+            serde_json::to_value(
+                MessageMcpRequest::new("server-1", "req-1", "tools/list").params(params)
+            )
+            .unwrap(),
             json!({
-                "connectionId": "conn-1",
+                "serverId": "server-1",
+                "requestId": "req-1",
                 "method": "tools/list",
                 "params": { "cursor": "abc" }
             })
         );
-        assert_eq!(
-            serde_json::to_value(DisconnectMcpRequest::new("conn-1")).unwrap(),
-            json!({ "connectionId": "conn-1" })
-        );
-        assert_eq!(
-            serde_json::to_value(MessageMcpNotification::new(
-                "conn-1",
-                "notifications/progress"
-            ))
-            .unwrap(),
-            json!({
-                "connectionId": "conn-1",
-                "method": "notifications/progress"
-            })
-        );
 
         let request_with_null_params: MessageMcpRequest = serde_json::from_value(json!({
-            "connectionId": "conn-1",
+            "serverId": "server-1",
+            "requestId": "req-1",
             "method": "tools/list",
-            "params": null
+            "params": null,
+            "_meta": null
         }))
         .unwrap();
         assert_eq!(request_with_null_params.params, None);
+        assert_eq!(request_with_null_params.meta, None);
+        for key in ["serverId", "requestId", "method"] {
+            let mut value =
+                json!({"serverId":"server-1", "requestId":"req-1", "method":"tools/list"});
+            value.as_object_mut().unwrap().remove(key);
+            assert!(serde_json::from_value::<MessageMcpRequest>(value).is_err());
+        }
+        for key in ["serverId", "requestId", "method"] {
+            let mut value =
+                json!({"serverId":"server-1", "requestId":"req-1", "method":"tools/list"});
+            value[key] = serde_json::Value::Null;
+            assert!(serde_json::from_value::<MessageMcpRequest>(value).is_err());
+        }
     }
 
     #[test]