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

Add zmcp as a dependency using zig fetch:

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

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.

License

AdjectiveAllison/zmcp

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