zig-utcp

zig-utcp provides a Universal Tool Calling Protocol (UTCP) implementation in Zig, with a focus on flexible transport layers (HTTP, CLI, MCP, SSE, WebSocket, and more) and tools loading via JSON or OpenAPI. The MCP component enables JSON-RPC style tool invocation over standard MCP channels (stdio or HTTP modes). You can use the included examples and transports to call tools, stream results, and apply post-processors, middleware, and rate limiting. The project emphasizes zero dependencies (pure Zig stdlib) and composable transports, so you can route tool calls through MCP for orchestration, or run a local MCP server that exposes your tools to clients via JSON-RPC.

To use the MCP capabilities, define your tools in UTCP format (id, name, description, and a transport-specific call_template) and then call them through the MCP transport. The repository provides example transports (HttpTransport, McpTransport, CliTransport, etc.) and utilities for streaming, post-processing, and middleware. If you want to experiment locally, the included MCP example demonstrates a JSON-RPC style flow over standard MCP channels and can be extended to fit your environment (e.g., running as a microservice behind an HTTP gateway or via a CLI tool for testing).

Prerequisites:

• Zig 0.15.2 or later installed on your system

Option A: Build from source (recommended for development)

1. Install Zig as per your platform (https://ziglang.org/download/).
2. Clone the repository: git clone https://github.com/bkataru/zig-utcp.git cd zig-utcp
3. Build the project and examples: zig build
4. Run examples to verify functionality (examples include MCP usage, HTTP, CLI, and streaming): zig build run-mcp zig build run-http zig build run-cli

Option B: Use Zig fetch (if you want to fetch as a dependency)

1. Fetch the library: zig fetch --save git+https://github.com/bkataru/zig-utcp.git
2. Integrate into a Zig project as a dependency via build.zig (see repository Quick Start for a template).

Option C: Local development with a local path dependency

1. In your build.zig, add a path dependency to the zig-utcp module as shown in the Quick Start section of the README.
2. Build and run your tool using the included examples as a reference.

Notes and tips:

• The MCP transport supports JSON-RPC style calls over standard MCP channels (stdio and HTTP modes).
• New in v0.2.0 includes CLI tool, middleware, circuit breaker, rate limiting, and post-processing features.
• The UTCP library emphasizes zero dependencies and composable transports; you can mix and match transports for different deployment scenarios.
• If you plan to expose MCP endpoints publicly, consider enabling authentication (API Key, Basic, Bearer, or OAuth2) via the Provider configuration.
• For testing tool definitions, the UTCP CLI tool (utcp) is available to load and inspect tools, and to exercise tool calls locally.