Pistom

A Model-Context-Protocol (MCP) Server for Piston

Pistom is a lightweight, zero-configuration server that connects any Model-Context-Protocol (MCP) compatible client (like an LLM agent) to the Piston API. It provides a secure and sandboxed environment for executing Python code on-demand.

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Table of Contents

• How It Works
• Key Features
• Usage
• Important Note: Rate Limiting
• Acknowledgements
• Contributing
• License

How It Works

Pistom acts as a simple, stateless proxy. It receives a code execution request from an MCP client, forwards it to the public Piston API, and then formats Piston's response back into the MCP specification for the client.

sequenceDiagram
    participant Client as LLM Client (MCP)
    participant Server as Pistom Server
    participant Piston as Piston API

    Client->>Server: Start Server Request
    activate Server
    Note over Client, Piston: Pistom is now listening for requests

    Client->>Server: Execute Code Request<br>{"code": "print(1+1)"}
    Server->>Piston: POST /api/v2/piston/execute<br>(with code and python settings)
    activate Piston

    Piston-->>Server: Raw JSON Response<br>{"run": {"output": "2\n", ...}}
    deactivate Piston

    Server-->>Client: Formatted MCP Response<br>[{"type": "text", "text": "2\n"}]
    deactivate Server

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Key Features

• On-Demand Code Execution: Instantly grant any LLM the ability to run Python code.
• Zero-Configuration: No API keys, sign-ups, or environment variables needed. It just works.
• Secure by Design: Code is executed in a remote, sandboxed environment provided by Piston, eliminating risks to your local machine.

Usage

Integrating with an MCP Client

To use Pistom with a compatible client, add it to the client's MCP server configuration. The client will then be able to start and communicate with Pistom automatically.

Here is the configuration snippet:

"pistom": {
    "url": "https://pistom.fastmcp.app/mcp"
}

That's it! Your client is now empowered with Python code execution capabilities.

Important Note: Rate Limiting

Warning

The public Piston API is rate-limited.

"The Piston API is rate limited to 5 requests per second..."
— Piston's documentation

Please be mindful of this limit in your applications.

Acknowledgements

Thanks to:

• Piston for the the free, public code execution engine.
• Model-Context-Protocol (MCP) for the protocol and SDK.

Contributing

Contributions are welcome! If you have a feature request, bug report, or pull request, please feel free to open an issue or submit a PR on the GitHub repository.

License

This project is licensed under the MIT License.