I rawdog a MCP server from scratch in Zig. No SDK
Some time ago I wanted to write a MCP server in Zig but found out there's no real JSON-RPC support in Zig, which MCP needs for communication. I ended up developing a JSON-RPC 2.0 library in Zig and more [1], which had its challenges. So I finally was able to put together a MCP server in Zig. It's built from scratch implementing the protocol messages from the MCP JSON schema. It's actually quite magical to have the LLM calling my MCP server [2]. The work is not too bad. Most of the hard work has already been done in the JSON-RPC library. [1]…
In plain words
This project provides a Model Context Protocol (MCP) server implementation built entirely in Zig without an SDK. The creator developed a JSON-RPC 2.0 library in Zig to enable MCP communication, then used it to build a MCP server from scratch by implementing protocol messages from the MCP JSON schema. The result allows large language models to call the MCP server directly. It targets developers working with Zig who need MCP server capabilities.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
Some time ago I wanted to write a MCP server in Zig but found out there's no real JSON-RPC support in Zig, which MCP needs for communication. I ended up developing a JSON-RPC 2.0 library in Zig and more [1], which had its challenges. So I finally was able to put together a MCP server in Zig. It's built from scratch implementing the protocol messages from the MCP JSON schema. It's actually quite magical to have the LLM calling my MCP server [2]. The work is not too bad. Most of the hard work has already been done in the JSON-RPC library. [1] https://github.com/williamw520/zigjr [2] https://github.com/williamw520/zigjr?tab=readme-ov-file#run-...
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