RMCP

use tokio::io::{stdin, stdout};
let transport = (stdin(), stdout());

The transport type must implemented IntoTransport trait, which allow split into a sink and a stream.

For client, the sink item is ClientJsonRpcMessage and stream item is ServerJsonRpcMessage

For server, the sink item is ServerJsonRpcMessage and stream item is ClientJsonRpcMessage

These types is automatically implemented IntoTransport trait

1. The types that already implement both Sink and Stream trait.
2. A tuple of sink Tx and stream Rx: (Tx, Rx).
3. The type that implement both [tokio::io::AsyncRead] and [tokio::io::AsyncWrite] trait.
4. A tuple of [tokio::io::AsyncRead] R and [tokio::io::AsyncWrite] W: (R, W).

For example, you can see how we build a transport through TCP stream or http upgrade so easily. examples

You can easily build a service by using ServerHandler or ClientHandler.

let service = common::counter::Counter::new();

// this call will finish the initialization process
let server = service.serve(transport).await?;

Once the server is initialized, you can send requests or notifications:

// request 
let roots = server.list_roots().await?;

// or send notification
server.notify_cancelled(...).await?;

let quit_reason = server.waiting().await?;
// or cancel it
let quit_reason = server.cancel().await?;

Check this file.

use rmcp::{ServerHandler, model::ServerInfo, schemars, tool};

use super::counter::Counter;

#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
pub struct SumRequest {
    #[schemars(description = "the left hand side number")]
    pub a: i32,
    #[schemars(description = "the right hand side number")]
    pub b: i32,
}
#[derive(Debug, Clone)]
pub struct Calculator;

// create a static toolbox to store the tool attributes
#[tool(tool_box)]
impl Calculator {
    // async function
    #[tool(description = "Calculate the sum of two numbers")]
    async fn sum(&self, #[tool(aggr)] SumRequest { a, b }: SumRequest) -> String {
        (a + b).to_string()
    }

    // sync function
    #[tool(description = "Calculate the difference of two numbers")]
    fn sub(
        &self,
        #[tool(param)]
        // this macro will transfer the schemars and serde's attributes
        #[schemars(description = "the left hand side number")]
        a: i32,
        #[tool(param)]
        #[schemars(description = "the right hand side number")]
        b: i32,
    ) -> String {
        (a - b).to_string()
    }
}

// impl call_tool and list_tool by querying static toolbox
#[tool(tool_box)]
impl ServerHandler for Calculator {
    fn get_info(&self) -> ServerInfo {
        ServerInfo {
            instructions: Some("A simple calculator".into()),
            ..Default::default()
        }
    }
}

The only thing you should do is to make the function's return type implement IntoCallToolResult.

And you can just implement IntoContents, and the return value will be marked as success automatically.

If you return a type of Result<T, E> where T and E both implemented IntoContents, it's also OK.