Tool not listed in response

[7sedam7]

Describe the bug
I'm trying to setup a basic MCP STDIO server with rmcp. I looked at their calculator example and made this:

use rmcp::{
    handler::server::wrapper::Json,
    model::{Implementation, ProtocolVersion, ServerCapabilities, ServerInfo},
    schemars, tool, tool_box, ServiceExt,
};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let server = TestService {};
    server.serve(rmcp::transport::stdio()).await?;

    Ok(())
}

#[derive(Debug, Clone)]
struct TestService {}

#[tool(tool_box)]
impl TestService {
    #[tool(description = "test")]
    fn get_documents(
        &self,
        #[tool(param)]
        #[schemars(description = "Search query")]
        search_query: String,
    ) -> Json<Vec<String>> {
        Json(vec!["test".to_string(), search_query])
    }

    //tool_box!(TestService { get_documents });
}

#[tool(tool_box)]
impl rmcp::ServerHandler for TestService {
    //tool_box!(@derive);
    fn get_info(&self) -> ServerInfo {
        ServerInfo {
            instructions: Some("test".to_string()),
            capabilities: ServerCapabilities::builder().enable_tools().build(),
            server_info: Implementation::from_build_env(),
            protocol_version: ProtocolVersion::LATEST,
        }
    }

    //fn list_tools(
    //    &self,
    //    request: Option<PaginatedRequestParam>,
    //    context: RequestContext<RoleServer>,
    //) -> ListToolsResult {
    //}
}

To test it I'm using: npx @modelcontextprotocol/inspector and my server is visible, however, no tool are returned.

I tried with #[tool(tool_box)] anotation, and this direct usage based on their example and mcp inspector always gets empty response for the list of tools...

I was trying to play with implementing list_tools myself, but it complains it's a dupplicate of this #[tool....] anotation, so i'm guessing that should automatically get the list of tools i annotated. (so i did not finish with manual list_tools implementation, signature was complicated.)

To Reproduce
Steps to reproduce the behavior:

1. Compile above code
2. build the release version
3. Run npx @modelcontextprotocol/inspector
4. Set path to release built under arguments and click connect
5. Look how initialize request (or if you click on tools) does not return get_documents function that is declaired as tool

Expected behavior
I expect my function to be listed as a tool...

I appologise if this is not a bug, but i don't understand how this is suppose to work. I'll appreciate explanation, or link to more info.

[jokemanfire]

you forget to start the handle thread .

    let service = server.serve(rmcp::transport::stdio()).await?;
    service.waiting().await;

[jokemanfire]

The document may not have been described clearly, so I will make revisions

[Jeadie]

I have the same issue even with this

let service = server.serve(rmcp::transport::stdio()).await?;
service.waiting().await;

[7sedam7]

Thanks for the comment, but same as Jeadie, i have the same issue after adding service.waiting().await?;

[jokemanfire]

Could you provide the system pls ? and with debug info ,use inspector may not get the info , you can choose the example client in examples.

 tracing_subscriber::fmt()
        .with_env_filter(EnvFilter::from_default_env().add_directive(tracing::Level::DEBUG.into()))
        .with_writer(std::io::stderr)
        .with_ansi(false)
        .init();

thanks.

[jokemanfire]

and my code

use rmcp::{
    handler::server::wrapper::Json,
    model::{Implementation, ProtocolVersion, ServerCapabilities, ServerInfo},
    schemars, tool, tool_box, ServiceExt,
};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let server = TestService {};
    let service = server.serve(rmcp::transport::stdio()).await?;
    service.waiting().await;
    Ok(())
}

#[derive(Debug, Clone)]
struct TestService {}

#[tool(tool_box)]
impl TestService {
    #[tool(description = "test")]
    fn get_documents(
        &self,
        #[tool(param)]
        #[schemars(description = "Search query")]
        search_query: String,
    ) -> Json<Vec<String>> {
        Json(vec!["test".to_string(), search_query])
    }

    //tool_box!(TestService { get_documents });
}

#[tool(tool_box)]
impl rmcp::ServerHandler for TestService {
    //tool_box!(@derive);
    fn get_info(&self) -> ServerInfo {
        ServerInfo {
            instructions: Some("test".to_string()),
            capabilities: ServerCapabilities::builder().enable_tools().build(),
            server_info: Implementation::from_build_env(),
            protocol_version: ProtocolVersion::LATEST,
        }
    }

    //fn list_tools(
    //    &self,
    //    request: Option<PaginatedRequestParam>,
    //    context: RequestContext<RoleServer>,
    //) -> ListToolsResult {
    //}
}

[jokemanfire]

and pls check the cargo.toml

rmcp = { git = "https://github.com/modelcontextprotocol/rust-sdk", branch = "main",features = ["server","transport-io","transport-sse-server","server"] }
tokio = { version = "1", features = ["full", "net"] }
serde_json = "1.0"
serde = { version = "1.0", features = ["derive"] }

[kyle-rader-msft]

I'm also trying to get started building MCP servers in Rust, and would love to use the "official MCP Rust SDK", however, running the example servers_std_io under the MCP Inspector, listing tools throws an error from the server and not getting a a valid tools response.
It appears that the ListToolsData is there, but something about the response is not matching the expected schema from Anthropic's MCP inspector, or from VSCode, or Cursor.

2025-05-15T18:55:25.941072Z DEBUG rmcp::service: new event evt=PeerMessage(Request(JsonRpcRequest { jsonrpc: JsonRpcVersion2_0, id: Number(7), request: ListToolsRequest(RequestOptionalParam { method: ListToolsRequestMethod, params: Some(PaginatedRequestParam { cursor: None }), extensions: Extensions }) })) 2025-05-

15T18:55:25.941177Z INFO rmcp::service: received request id=7 request=ListToolsRequest(RequestOptionalParam { method: ListToolsRequestMethod, params: Some(PaginatedRequestParam { cursor: None }), extensions: Extensions }) 

2025-05-15T18:55:25.941448Z INFO rmcp::service: response message id=7 result=ListToolsResult(ListToolsResult { next_cursor: None, tools: [Tool { name: "echo", description: Some("Repeat what you say"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "properties": Object {"saying": Object {"description": String("Repeat what you say"), "type": String("string")}}, "required": Array [String("saying")], "title": String("__ECHOToolCallParam"), "type": String("object")}, annotations: None }, Tool { name: "sum", description: Some("Calculate the sum of two numbers"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "properties": Object {"a": Object {"format": String("int32"), "type": String("integer")}, "b": Object {"format": String("int32"), "type": String("integer")}}, "required": Array [String("a"), String("b")], "title": String("StructRequest"), "type": String("object")}, annotations: None }, Tool { name: "get_value", description: Some("Get the current counter value"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "title": String("EmptyObject"), "type": String("object")}, annotations: None }, Tool { name: "decrement", description: Some("Decrement the counter by 1"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "title": String("EmptyObject"), "type": String("object")}, annotations: None }, Tool { name: "increment", description: Some("Increment the counter by 1"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "title": String("EmptyObject"), "type": String("object")}, annotations: None }, Tool { name: "say_hello", description: Some("Say hello to the client"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "title": String("EmptyObject"), "type": String("object")}, annotations: None }] }) 

2025-05-15T18:55:25.941574Z DEBUG rmcp::service: new event evt=ToSink(Response(JsonRpcResponse { jsonrpc: JsonRpcVersion2_0, id: Number(7), result: ListToolsResult(ListToolsResult { next_cursor: None, tools: [Tool { name: "echo", description: Some("Repeat what you say"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "properties": Object {"saying": Object {"description": String("Repeat what you say"), "type": String("string")}}, "required": Array [String("saying")], "title": String("__ECHOToolCallParam"), "type": String("object")}, annotations: None }, Tool { name: "sum", description: Some("Calculate the sum of two numbers"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "properties": Object {"a": Object {"format": String("int32"), "type": String("integer")}, "b": Object {"format": String("int32"), "type": String("integer")}}, "required": Array [String("a"), String("b")], "title": String("StructRequest"), "type": String("object")}, annotations: None }, Tool { name: "get_value", description: Some("Get the current counter value"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "title": String("EmptyObject"), "type": String("object")}, annotations: None }, Tool { name: "decrement", description: Some("Decrement the counter by 1"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "title": String("EmptyObject"), "type": String("object")}, annotations: None }, Tool { name: "increment", description: Some("Increment the counter by 1"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "title": String("EmptyObject"), "type": String("object")}, annotations: None }, Tool { name: "say_hello", description: Some("Say hello to the client"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "title": String("EmptyObject"), "type": String("object")}, annotations: None }] }) }))

[kyle-rader-msft]

Update: This is what I was missing:

#[tool(tool_box)]
impl ServerHandler for MyToolBox {
    fn get_info(&self) -> ServerInfo {
        ServerInfo {
            instructions: Some("My toolbox".into()),
            capabilities: ServerCapabilities::builder().enable_tools().build(), # ⚠️ <= Enable Tools!
            ..Default::default()
        }
    }
}

[jokemanfire]

2025-05-15T18:55:25.941574Z DEBUG rmcp::service: new event evt=ToSink(Response(JsonRpcResponse { jsonrpc: JsonRpcVersion2_0, id: Number(7), result: ListToolsResult(ListToolsResult { next_cursor: None, tools: [Tool { name: "echo", description: Some("Repeat what you say"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "properties": Object {"saying": Object {"description": String("Repeat what you say"), "type": String("string")}}, "required": Array [String("saying")], "title": String("__ECHOToolCallParam"), "type": String("object")}, annotations: None }, Tool { name: "sum", description: Some("Calculate the sum of two numbers"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "properties": Object {"a": Object {"format": String("int32"), "type": String("integer")}, "b": Object {"format": String("int32"), "type": String("integer")}}, "required": Array [String("a"), String("b")], "title": String("StructRequest"), "type": String("object")}, annotations: None }, Tool { name: "get_value", description: Some("Get the current counter value"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "title": String("EmptyObject"), "type": String("object")}, annotations: None }, Tool { name: "decrement", description: Some("Decrement the counter by 1"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "title": String("EmptyObject"), "type": String("object")}, annotations: None }, Tool { name: "increment", description: Some("Increment the counter by 1"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "title": String("EmptyObject"), "type": String("object")}, annotations: None }, Tool { name: "say_hello", description: Some("Say hello to the client"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "title": String("EmptyObject"), "type": String("object")}, annotations: None }] }) }))

Is this main branch?

[jokemanfire]

I've test this project in cursor and newest inspector, but there's no problem .mcp-containerd .

[4t145]

@jokemanfire I can add a debug feature to log git commit hash and cargo package version if there is.