#MoonBit MCP SDK

#Installation

moon add colmugx/mcp

#Quick Start

#Server

async fn main {
  @mcp.MCPServer::MCPServer("demo-server", "1.0.0")
    .tool("echo", "Echo text", Json::object({}), fn(args) {
      let text = match args {
        Object(obj) =>
          match obj.get("text") {
            Some(String(value)) => value
            _ => ""
          }
        _ => ""
      }
      Ok(@tool.ToolResult::text(text))
    })
    .run_stdio()
}

#Client

async fn main {
  match @mcp.MCPClient::connect_http(
    url="http://localhost:4240/mcp",
    name="demo-client",
    version="1.0.0",
  ) {
    Ok(client) => {
      // Optional one-shot discovery of server identity/capabilities.
      ignore(client.discover())
      match client.list_tools() {
        Ok(result) => for tool in result.tools { println(tool.name) }
        Err(e) => println(e.message())
      }
      client.close()
    }
    Err(e) => println("connect failed: \{e.message()}")
  }
}

#Host

async fn main {
  let host = @mcp.MCPHost::MCPHost(name="my-host", version="1.0.0")
  @async.with_task_group(group => {
    ignore(host.connect_stdio(name="local", cmd="moon", args=["run", "server"], group~))
    ignore(host.connect_http(name="remote", url="http://localhost:4240/mcp"))
    match host.list_tools() {
      Ok(result) => for tool in result.tools { println(tool.name) } // local.echo
      Err(e) => println(e.message())
    }
    ignore(host.call_tool("local.echo", arguments="{\"text\":\"hello\"}"))
    host.close_all()
  })
}

#Documentation

#API Direction

• MCPServer for serving tools, resources, and prompts.
• MCPClient for one server connection.
• MCPHost for multiple named server connections.
• colmugx/mcp/client/legacy for talking to 2025-11-25-era servers (LegacyClient).

#License