MCP Tool Builder

The MCP Tool Builder is a lightweight server that turns natural‑language descriptions into executable tools for large language models. It addresses the challenge of extending an AI assistant’s capabilities on‑the‑fly: developers can ask a model to “create a tool that pulls the current Bitcoin price from CoinGecko” and the server will generate, store, and expose a fully‑functional Python script that Claude Desktop can call. This eliminates the need for manual scripting or redeploying tool libraries every time a new requirement arises.

At its core, the server listens for the command issued by an MCP client. When a request arrives, it parses the description, writes a minimal Python module in a dedicated directory, and updates a JSON manifest that lists all available tools. The generated code is immediately discoverable by the MCP client, though a client restart (e.g., restarting Claude Desktop) is required for the new tool to appear in the UI. Existing tools—such as and —demonstrate the format: concise, single‑purpose functions that return structured data to the model.

Key features include:

• Dynamic tool creation from plain English, enabling rapid prototyping and iteration.
• Persistent storage of tool scripts and metadata in a predictable file structure, simplifying version control and debugging.
• Seamless integration with MCP‑enabled assistants like Claude Desktop, where the newly created tool becomes part of the assistant’s action repertoire after a brief restart.
• Modular design that allows developers to extend or replace the tool generation logic without touching the core server.

Real‑world use cases span from rapid API integration—such as adding a new financial data fetcher—to internal tooling, where developers can quickly prototype utilities for data extraction or transformation. In an AI‑driven workflow, a user might ask the assistant to “create a tool that summarizes a PDF” and immediately have that capability available, reducing friction between idea and implementation.

The standout advantage of MCP Tool Builder is its on‑demand nature: developers no longer need to pre‑define a comprehensive toolset. Instead, they can let the model dictate what is needed next, generate it instantly, and have it ready for execution. This agility accelerates feature development, lowers the barrier to experimentation, and keeps the assistant’s tool library aligned with evolving user needs.