Defining tools with MCP

🧠 Notes: Building an MCP Server with Tools

**I. Overview of the MCP Server**

• Purpose: To add functionality (tools) to the existing CLI chat bot.
• Location: The server implementation resides in MCP server. py within the root project directory.
• Initial Setup: The server starts with an in-memory collection of documents (stored in a dictionary, docs).

**II. Using the MCP Python SDK**

• Benefit: The official MCP Python SDK simplifies server creation and tool definition significantly.
• Server Creation: The SDK allows for the creation of the MCP server with minimal code (one line).
• Tool Definition: Instead of manually writing complex JSON schemas, the SDK allows tools to be defined using standard Python syntax.
• Process: When a tool is defined in Python, the MCP SDK automatically generates the necessary tool JSON schema for use with Bedrock.

**III. Implementing Tools (General Procedure)**

• Goal: Define a tool's name, description, required arguments, and the actual function logic.
• Tool Definition Structure:
• Use MCP. tool to define the tool.
• Provide a clear name and description.
• Define the function that executes the tool's logic.
• Argument Handling: Arguments are defined using field from Pydantic (e. g. , field(description="... ")).

**IV. Tool Implementation Examples**

**A. Tool 1: Reading Document Contents (read_doc_contents)**

• Goal: Take a document ID and return its contents.
• Logic:
• Check if the provided doc_id exists as a key in the docs dictionary.
• If not found, raise a ValueError (e. g. , "doc with ID [doc_id] not found").
• If found, return the corresponding document content (docs[doc_id]).

**B. Tool 2: Editing Document Contents (edit_document)**

• Goal: Perform a find-and-replace operation within a document.
• Arguments Required:
• doc_id (string): ID of the document to edit.
• old_string (string): The exact text to find (including whitespace).
• new_string (string): The text to replace the old string with.
• Logic:
• Check if the doc_id exists in the docs dictionary.
• If found, execute the replacement: docs[doc_id] = docs[doc_id]. replace(old_string, new_string).
• Handle the case where the document ID is not found by raising a ValueError.

Takeaways

• Le serveur MCP sert à ajouter des fonctionnalités (outils) au chatbot CLI et est implémenté dans MCP server. py.
• Le SDK Python MCP simplifie la création de serveurs et de définitions d'outils en utilisant la syntaxe Python au lieu de schémas JSON complexes.
• Pour définir un outil, on utilise MCP. tool en fournissant un nom, une description et la logique de fonction.
• La gestion des arguments des outils est assurée par field de Pydantic.
• Les outils manipulent une collection de documents en mémoire (docs) pour lire ou modifier le contenu.