A Swift implementation of the MCP (Model Context Protocol) for JSON-RPC over various transports.
- 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
Add SwiftMCP as a dependency in your Package.swift:
dependencies: [
.package(url: "https://github.com/Cocoanetics/SwiftMCP.git", branch: "main")
]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 --openapiWhen using HTTP+SSE transport with the --token option, clients must include an Authorization header with their requests:
Authorization: Bearer your-secret-tokenThe --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.
To implement your own MCP server:
- Attach the
@MCPServermacro to a reference type like class or actor - Define your tools using
@MCPToolattribute - 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()The @MCPServer and @MCPTool macros extract documentation comments to describe class, parameters and return value.
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 theDemos/SwiftMCPDemo/Calculator.swiftfile, where theCalculatoractor 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 theDemos/SwiftMCPDemo/Calculator.swiftfile, where various functions such asadd,subtract,testArray,multiply,divide,greet,ping, andnoopare annotated with@MCPTool.@MCPResource: This macro is used to expose read-only data through URI templates. Resources allow clients to access data using structured URIs with path and query parameters. The macro automatically generates the necessary infrastructure to match URIs against templates and extract parameters.
The @MCPResource macro allows you to expose functions as resources that can be accessed via URI patterns:
@MCPServer(name: "ResourceServer")
actor ResourceServer {
/// Get user profile by ID
@MCPResource("users://{user_id}/profile")
func getUserProfile(user_id: Int) -> String {
return "Profile for user \(user_id)"
}
/// Search users with pagination
@MCPResource("users://search?q={query}&page={page}", mimeType: "application/json")
func searchUsers(query: String, page: Int = 1) -> String {
return """
{"query": "\(query)", "page": \(page), "results": [...]}
"""
}
}Key features:
- URI Templates: Define patterns with placeholders in curly braces
{param} - Path Parameters: Extract values from the URI path (e.g.,
/users/{id}) - Query Parameters: Extract values from query strings (e.g.,
?page={page}) - Optional Parameters: Support default values for optional parameters
- MIME Types: Optionally specify content type with
mimeTypeparameter - Type Safety: Parameters are automatically converted to the correct Swift types
The server automatically provides:
- Resource discovery through
mcpResourceTemplates - URI matching and parameter extraction
- Type conversion and validation
- Error handling for missing or invalid parameters
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.
This project is licensed under the BSD 2-clause License - see the LICENSE file for details.