zmcp - a Zig MCP Library

A lightweight Zig implementation of the Model Context Protocol (MCP). ZMCP enables seamless integration between LLM applications and external tools through compile-time validated interfaces.

Features

• Type-Safe Tools: Struct-based parameters with compile-time validation
• Automatic Resource Management: Allocator injection for heap-using tools
• Error Conversion: Zig errors automatically converted to MCP error responses
• Transport Layer: Current support for stdio transport (HTTP+SSE planned)
• MCP Features:
  • ✅ Tools API with full schema generation
  • ✅ Basic logging support
  • ✅ Progress tracking
  • ⏳ Resources API (planned)
  • ⏳ Prompts API (planned)

Installation

1. Add zmcp as a dependency using zig fetch:

# Latest version
zig fetch --save git+https://github.com/AdjectiveAllison/zmcp.git#main

2. Add zmcp as a module in your build.zig:

const zmcp_dep = b.dependency("zmcp", .{
    .target = target,
    .optimize = optimize,
});
const zmcp = zmcp_dep.module("zmcp");

// Add to your executable
exe.root_module.addImport("zmcp", zmcp);

Quick Start

const EchoParams = struct {
    allocator: std.mem.Allocator, // Auto-injected by server
    message: []const u8,
    repeat: u32 = 1 // Default value
};

fn echoFn(params: EchoParams) ![]const u8 {
    // ... implementation using params.allocator
}

const echo_tool = zmcp.Tool(
    "echo",
    "Echo with repetition",
    echoFn // Struct-based handler
);

Structured Parameters

Tools must use a struct parameter containing:

• An optional allocator field (auto-injected)
• Typed parameters with validation
• Optional fields with default values
• struct keys turn into names for the tool call parameters

Example parameter struct:

const ProcessArgs = struct {
    allocator: std.mem.Allocator,
    input: []const u8,
    iterations: u32 = 10,
    verbose: ?bool = null
};

Current Limitations

• Only stdio transport supported (HTTP+SSE planned)
• Resources and Prompts APIs not yet implemented
• Limited to JSON-compatible Zig types
• No support for custom transports

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under the MIT License - see the LICENSE file for details.