mcpkit-macros 0.5.0

Procedural macros for mcpkit
Documentation

mcpkit-macros

Procedural macros for the Model Context Protocol (MCP) SDK.

This crate provides the unified #[mcp_server] macro that simplifies MCP server development by eliminating boilerplate.

Overview

The macro system provides:

Macro Purpose
#[mcp_server] Transform an impl block into a full MCP server
#[tool] Mark a method as an MCP tool
#[resource] Mark a method as an MCP resource handler
#[prompt] Mark a method as an MCP prompt handler

Usage

use mcpkit::prelude::*;

struct Calculator;

#[mcp_server(name = "calculator", version = "1.0.0")]
impl Calculator {
    /// Add two numbers together
    #[tool(description = "Add two numbers")]
    async fn add(&self, a: f64, b: f64) -> ToolOutput {
        ToolOutput::text((a + b).to_string())
    }

    /// Multiply two numbers
    #[tool(description = "Multiply two numbers")]
    async fn multiply(&self, a: f64, b: f64) -> ToolOutput {
        ToolOutput::text((a * b).to_string())
    }
}

#[tokio::main]
async fn main() -> Result<(), McpError> {
    Calculator.serve_stdio().await
}

Attributes

#[mcp_server]

Attribute Required Description
name Yes Server name
version Yes Server version (can use env!("CARGO_PKG_VERSION"))
instructions No Usage instructions sent to clients
capabilities No List of capabilities to advertise

#[tool]

Attribute Required Description
description Yes Tool description for clients
name No Override the method name
destructive No Mark tool as destructive
idempotent No Mark tool as idempotent

Generated Code

The #[mcp_server] macro generates:

  1. impl ServerHandler with server_info() and capabilities()
  2. impl ToolHandler with list_tools() and call_tool() (if any #[tool] methods)
  3. impl ResourceHandler (if any #[resource] methods)
  4. impl PromptHandler (if any #[prompt] methods)
  5. A serve_stdio() convenience method

Code Reduction

This single macro replaces multiple manual implementations, significantly reducing boilerplate compared to implementing handler traits directly.

Part of mcpkit

This crate is part of the mcpkit SDK. For most use cases, depend on mcpkit directly rather than this crate.

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.