SwiftMCP

A Swift implementation of the MCP (Model Context Protocol) for JSON-RPC over various transports.

Features

• Multiple transport options:
  • Standard I/O (stdio) for command-line usage
  • HTTP+SSE (Server-Sent Events) for web applications
• JSON-RPC 2.0 compliant
• Asynchronous response handling via SSE
• Built-in authorization support
• Cross-platform compatibility

Installation

Add SwiftMCP as a dependency in your Package.swift:

dependencies: [
    .package(url: "https://github.com/Cocoanetics/SwiftMCP.git", branch: "main")
]

Usage

Command Line Demo

The included demo application shows how to use SwiftMCP with different transport options:

# Using stdio transport
SwiftMCPDemo stdio

# Using HTTP+SSE transport
SwiftMCPDemo httpsse --port 8080

# Using HTTP+SSE with authorization
SwiftMCPDemo httpsse --port 8080 --token your-secret-token

# Using HTTP+SSE with OpenAPI support
SwiftMCPDemo httpsse --port 8080 --openapi

# Using HTTP+SSE with authorization and OpenAPI support
SwiftMCPDemo httpsse --port 8080 --token your-secret-token --openapi

When using HTTP+SSE transport with the --token option, clients must include an Authorization header with their requests:

Authorization: Bearer your-secret-token

OpenAPI support

The --openapi option enables OpenAPI endpoints for AI plugin integration. When this option is used, the server will provide an OpenAPI specification at /openapi.json and an AI plugin manifest at /.well-known/ai-plugin.json. This allows for easy integration with AI models and other tools that support OpenAPI.

Custom Server Implementation

To implement your own MCP server:

1. Attach the @MCPServer macro to a reference type like class or actor
2. Define your tools using @MCPTool attribute
3. Choose and configure a transport

Example:

@MCPServer
class MyServer {
    @MCPTool
    func add(a: Int, b: Int) -> Int {
        return a + b
    }
}

// Using HTTP+SSE transport with authorization
let server = MyServer()
let transport = HTTPSSETransport(server: server, port: 8080)

// Optional: Add authorization
transport.authorizationHandler = { token in
    guard let token = token, token == "your-secret-token" else {
        return .unauthorized("Invalid token")
    }
    return .authorized
}

try transport.run()

Documentation Extraction

The @MCPServer and @MCPTool macros extract documentation comments to describe class, parameters and return value.

Macros Functionality

The macros in this repository provide functionality for defining and exposing tools and servers in the SwiftMCP framework. Here are the main functionalities of the macros:

• @MCPServer: This macro is used to define a class or actor as an MCP server. It extracts documentation comments to describe the class, parameters, and return values. An example of its usage can be seen in the Demos/SwiftMCPDemo/Calculator.swift file, where the Calculator actor is annotated with @MCPServer(name: "SwiftMCP Demo").
• @MCPTool: This macro is used to define functions within an MCP server that can be called as tools. It also extracts documentation comments to describe the function, parameters, and return values. Examples of its usage can be seen in the Demos/SwiftMCPDemo/Calculator.swift file, where various functions such as add, subtract, testArray, multiply, divide, greet, ping, and noop are annotated with @MCPTool.

These macros help in automatically generating the necessary metadata and documentation for the MCP server and its tools, making it easier to expose them for JSON-RPC communication and integration with AI models.

License

This project is licensed under the BSD 2-clause License - see the LICENSE file for details.