MCP Swift SDK

Swift implementation of the Model Context Protocol (MCP).

Requirements

• Swift 6.0+ (Xcode 16+)

See the Platform Availability section below for more information about platform requirements.

Installation

Swift Package Manager

Add the following to your Package.swift file:

dependencies: [
    .package(url: "https://github.com/modelcontextprotocol/swift-sdk.git", from: "0.7.1")
]

Usage

Basic Client Setup

import MCP

// Initialize the client
let client = Client(name: "MyApp", version: "1.0.0")

// Create a transport and connect
let transport = StdioTransport()
try await client.connect(transport: transport)

// Initialize the connection
let result = try await client.initialize()

Basic Server Setup

import MCP

// Initialize the server with capabilities
let server = Server(
    name: "MyServer", 
    version: "1.0.0",
    capabilities: .init(
        prompts: .init(),
        resources: .init(
            subscribe: true
        ),
        tools: .init()
    )
)

// Create transport and start server
let transport = StdioTransport()
try await server.start(transport: transport)

// Register method handlers
server.withMethodHandler(ReadResource.self) { params in
    // Handle resource read request
    let uri = params.uri
    let content = [Resource.Content.text("Example content")]
    return .init(contents: content)
}

// Register notification handlers
server.onNotification(ResourceUpdatedNotification.self) { message in
    // Handle resource update notification
}

// Stop the server when done
await server.stop()

Working with Tools

// List available tools
let tools = try await client.listTools()

// Call a tool
let (content, isError) = try await client.callTool(
    name: "example-tool", 
    arguments: ["key": "value"]
)

// Handle tool content
for item in content {
    switch item {
    case .text(let text):
        print(text)
    case .image(let data, let mimeType, let metadata):
        // Handle image data
    }
}

Working with Resources

// List available resources
let (resources, nextCursor) = try await client.listResources()

// Read a resource
let contents = try await client.readResource(uri: "resource://example")

// Subscribe to resource updates
try await client.subscribeToResource(uri: "resource://example")

// Handle resource updates
await client.onNotification(ResourceUpdatedNotification.self) { message in
    let uri = message.params.uri
    let content = message.params.content
    // Handle the update
}

Working with Prompts

// List available prompts
let (prompts, nextCursor) = try await client.listPrompts()

// Get a prompt with arguments
let (description, messages) = try await client.getPrompt(
    name: "example-prompt",
    arguments: ["key": "value"]
)

Platform Availability

The Swift SDK has the following Apple platform requirements:

While the core library works on any platform supporting Swift 6 (including Linux and Windows), running a client or server requires a compatible transport.

MCP's transport layer handles communication between clients and servers. The Swift SDK provides multiple built-in transports:

• StdioTransport: Implements stdio transport. Available on Apple platforms and Linux distributions with glibc (Ubuntu, Debian, Fedora, CentOS, RHEL).
• HTTPClientTransport: Implements Streamable HTTP transport using Foundation URL Loading System
• NetworkTransport: Implements custom transport over TCP and UDP using Apple's Networking framework. Available exclusively on Apple platforms.

You can implement a custom transport for platforms without built-in support. [^1]

For custom transport implementation details, see the Transport protocol.

[^1]: We're working to add stdio transport support for Alpine Linux and Windows. If you're interested in either of those platforms, please take a look at their respective PRs and leave a comment!

Changelog

This project follows Semantic Versioning. For pre-1.0 releases, minor version increments (0.X.0) may contain breaking changes.

For details about changes in each release, see the GitHub Releases page.

License

This project is licensed under the MIT License.