Pharo MCP Server

An MCP protocol server implemented in Pharo, connecting LLMs and Pharo applications

Developer tools Artificial intelligence chatbots #LLM Tooling #Protocol Bridging #Pharo Services

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update time : 2025-04-28

What is the Pharo MCP Server?

The Pharo MCP Server is a standardized tool that allows large language models (such as Claude) to interact with applications in the Pharo Smalltalk environment through the Anthropic Model Context Protocol (MCP).

How to Use the Pharo MCP Server?

You can configure and start the server in just a few steps to enable your Pharo applications to support the MCP protocol.

Applicable Scenarios

It is suitable for developers who need to integrate the capabilities of large language models, such as dynamically generating code, performing complex tasks, or providing intelligent suggestions.

Main Features

MCP Protocol CompatibilitySupports the standard MCP protocol, including service discovery, tool description, and tool invocation.

Dynamic Tool RegistrationAllows developers to easily register Pharo methods or blocks as MCP tools.

Automatic Service DescriptionAutomatically generates the MCP service description JSON file based on the registered tools.

Advantages and Limitations

Advantages

Supports the standardized MCP protocol, simplifying integration.

Dynamic tool registration, offering high flexibility.

Developed based on Pharo Smalltalk, seamlessly integrating with the existing ecosystem.

Built - in JSON parsing and generation tools, improving reliability.

Limitations

Requires a certain level of programming ability from developers.

May require additional configuration to adapt to specific application scenarios.

Currently in the early development stage, and some features are yet to be perfected.

How to Use

Install the Pharo MCP Server

Load the MCP server in the Pharo environment and install it through the Metacello tool.

Define and register the tools that need to be exposed to MCP.

Start the Server

Configure and start the server to listen for MCP requests.

Usage Examples

Example 1: Invoke the Greeting ToolInvoke the Greeting tool through MCP and get a personalized greeting.

Example 2: Query the DatabaseUse the MCP tool to query the database and return the results.

Frequently Asked Questions

How to Ensure the Security of Tools?

Does it Support Multiple Tools Running Simultaneously?

Related Resources

Pharo MCP Server GitHub Repository

View the source code and contribution guidelines.

Model Context Protocol Official Documentation

Understand the detailed specifications of the MCP protocol.

Pharo Smalltalk Official Website

Learn more about Pharo Smalltalk.

🚀 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.

Ensure Metacello is loaded in your Pharo image (usually already loaded).
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:

Discovery: How an LLM knows whether a service supports MCP and obtains basic information.
Service Description: How a service describes its available tools (functions), including the tool's name, purpose, input parameters, and output format.
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.