Pharo MCP Server

🚀 Pharo MCP Server

An implementation of Anthropic's Model Context Protocol (MCP) server specification in Pharo Smalltalk. Enables LLMs (e.g., Claude) to interact with Pharo applications.

🚀 Quick Start

The Pharo MCP Server is an implementation of Anthropic's Model Context Protocol (MCP) server specification in Pharo Smalltalk. It allows LLMs like Claude to interact with Pharo applications.

✨ Features

• MCP Specification Compliance: Implements core server - side endpoints:
  • Discovery (/.well - known/model - context)
  • Service description (/mcp/description - or configurable path)
  • Invocation (/mcp/invoke - or configurable path)
• Dynamic Tool Registration: Provides a simple API to register Pharo methods or code blocks as MCP tools.
• Automatic Service Description Generation: Generates MCP service description JSON based on registered tools and their metadata (name, description, schema).
• Web Server Integration: Based on the [Teapot](https://github.com/pharo - web/teapot) micro - web framework.
• JSON Processing: Uses NeoJSON for powerful JSON parsing and generation.
• Scalability: Designed to be integrated into larger Pharo applications.
• (Planned): Input validation of tool parameters using JSON schema definition.
• (Planned): Assistants to integrate common Pharo object models (e.g., using [Voyage](https://github.com/pharo - nosql/voyage)).

📦 Installation

This project is intended to be loaded via Metacello.

1. Ensure Metacello is loaded in your Pharo image (usually already loaded).
2. Execute the following code in the Pharo workspace (adjust the repository URL and branch/tag as needed):

Metacello new
    baseline: 'MCPFramework'; "<- Use your actual baseline class name (without 'BaselineOf')"
    repository: 'github://YOUR_USERNAME/pharo - mcp - server:main/'; "<- Change to this repository URL and branch/tag"
    load.

📚 Documentation

What is MCP?

The Model Context Protocol (MCP) is a specification developed by Anthropic, aiming to standardize the interaction between large language models (LLMs) and their external tools and services. It defines the following mechanisms:

1. Discovery: How an LLM knows whether a service supports MCP and obtains basic information.
2. Service Description: How a service describes its available tools (functions), including the tool's name, purpose, input parameters, and output format.
3. Invocation: How an LLM securely invokes a tool through a specific protocol, passes the required parameters, and receives the results. The goal is to make LLM tool usage more reliable, secure, and standardized. For more detailed information, please refer to the official Model Context Protocol GitHub organization.

Goal of this Project

This project aims to provide a powerful and easy - to - use server - side implementation of the MCP specification for the Pharo Smalltalk environment. It allows developers to expose the functions in their Pharo applications (such as querying data, creating objects, triggering operations) as "tools", enabling MCP - compatible LLMs (e.g., Claude 3) to discover and invoke these tools through a standardized protocol. This bridges the gap between the Pharo environment and modern LLM capabilities.

Defining Tools

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Configuration

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Development & Contributing

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📄 License

This project is licensed under the MIT License.