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
- TCP+Bonjour for local discovery over raw TCP
- JSON-RPC 2.0 compliant with OpenAPI generation
- Built-in authorization and optional OAuth validation
- Transparent OAuth proxy mode for MCP and OpenAPI
- Cross-platform compatibility

Server Features

- Tools – expose functions with @MCPTool
- Resources – publish data with @MCPResource
- Prompts – build prompts using @MCPPrompt
- Utilities
- Progress notifications via RequestContext.current
- Structured logging streamed through Session.current
- Completion suggestions for parameters (defaults for Bool and CaseIterable)

Client Features

- Roots – dynamic filesystem roots announced by the client
- Sampling – request small previews of client files

Installation

Add SwiftMCP as a dependency in your Package.swift:

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

Package traits

SwiftMCP exposes its optional feature areas as SwiftPM package traits, all enabled by default — existing consumers and a plain swift build are unaffected. The single import SwiftMCP module is unchanged.

| Trait | Enables | Extra dependencies |
| --- | --- | --- |
| Server | HTTP/SSE + TCP server transports | swift-nio, swift-crypto, swift-certificates |
| Client | The MCP client (MCPServerProxy) | — |
| OpenAPI | OpenAPI / AI-plugin manifest models and routes | — |

The tool/schema foundation — JSONValue, JSONSchema, MCPToolProviding, the @MCPTool / @MCPServer macros, errors — is always-on core and needs no trait.

Disabling Server drops swift-nio (and swift-crypto/swift-certificates) entirely, which makes the package build on Windows and gives client/tools-only consumers a lighter graph. A consumer that only talks to remote MCP servers selects just what it needs (your manifest must be swift-tools-version: 6.1 or newer to choose traits):

.package(
    url: "https://github.com/Cocoanetics/SwiftMCP.git",
    branch: "main",
    traits: ["Client"]   // tool/schema core + client, no swift-nio
)

> AppIntents bridging (@MCPAppIntentTool, AppShortcuts discovery) is not a trait: it is already gated by #if canImport(AppIntents), so it is automatically excluded on platforms without AppIntents (Linux, Windows, Android).

Usage

Command Line Demo

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

```bash