py-exec-mcp

# py-exec-mcp **Run Python from an MCP client without a shell mangling your code.** [](https://github.com/blurxy/py-exec-mcp/actions/workflows/ci.yml) [](https://pypi.org/project/py-exec-mcp/) [](https://pypi.org/project/py-exec-mcp/) [](LICENSE) --- ## The problem Ask an agent to run a one-liner and it reaches for `python -c "..."`. That code passes through **three parsers** before Python ever sees it — the shell, argv splitting, then Python itself — each with its own escaping rules. ```bash python -c "print(f'he said \"hi {name}\"')" # which layer eats which quote? ``` The failure mode is what makes this worth fixing: **you usually get a wrong answer, not an error.** A backslash vanishes, a quote closes early, an f-string silently becomes a literal — and the output looks plausible. So the agent retries with different escaping, or falls back to writing a temp file and running it, every single time. ## The fix Code arrives as a JSON string in the MCP tool call and is handed to the interpreter over **stdin** (`python -`). No shell. No argv. Nothing re-parses it. Write the code exactly as it would appear in a `.py` file — nested quotes, f-strings, backslashes, regex, triple-quoted blocks — and it arrives verbatim. ## Install ```bash uvx py-exec-mcp # no install pip install py-exec-mcp # or the usual way uvx --from git+https://github.com/blurxy/py-exec-mcp py-exec-mcp # straight from main ``` Works on **both MCP SDK majors** — 2.x renamed `FastMCP` to `MCPServer`, and the server binds whichever one your environment has, so you are not forced to pin the SDK to match it. Needs `mcp>=1.19`. ## Configure <details open> <summary><b>Claude Code</b> — <code>.mcp.json</code> in your project root…