Implementing a client

📝 Notes: MCP Client Implementation

**I. Overview of the MCP Client**

• Purpose: The MCP Client (found in mcp-client. py) acts as a wrapper around the MCP Python SDK's ClientSession.
• Function: It exposes server functionality (like tools and prompts) to the rest of the codebase.
• Design: The client is a larger class designed to manage resources and simplify the cleanup process associated with the underlying ClientSession.
• Dual Role: This project demonstrates both client and server implementation simultaneously.

**II. Core Components and Concepts**

• ClientSession: This is the actual connection to the MCP server, provided by the MCP Python SDK.
• Resource Management: The client class handles necessary resource cleanup (e. g. , when the program closes or the connection is no longer needed), which is implemented in functions like connect, cleanup_async_enter, and cleanup_async_exit.
• Client Functionality: The client allows the application to:
• List available tools on the server.
• Execute (call) a specific tool on the server.

**III. Key Functions Implemented**

• list_tools():
• Action: Calls self. session. list_tools().
• Result: Returns a list of all tools defined by the MCP server.
• call_tool(tool_name, tool_input):
• Action: Calls self. session. call_tool(tool_name, tool_input).
• Result: Executes the specified tool on the server, passing the required input arguments.

**IV. Important Considerations (Gotchas)**

• Tool Definition Structure: The structure of a tool's input schema provided by the MCP spec is slightly different from the structure expected by Bedrock JSON schema.
• Translation Step: The code must automatically convert the MCP tool definition into the exact structure required by Bedrock (this conversion is handled by the two_bedrock_tools function in bedrock. py).
• Testing: The client can be tested directly by running python mcp_client. py to establish a connection and run commands against the server.

**V. Workflow Summary**

• The client lists tools → Tools are retrieved.
• The client calls a tool → The server executes the tool.
• The application uses the client to provide tools to Claude → Claude decides to use a tool → The client executes the tool on the server.

Takeaways

• Le client MCP agit comme une enveloppe (wrapper) autour de ClientSession pour simplifier la gestion des ressources et exposer les fonctionnalités du serveur.
• Les deux fonctions clés sont list_tools() pour récupérer la liste des outils et call_tool(nom, entrée) pour les exécuter.
• Une étape de conversion est indispensable pour traduire le schéma des outils MCP vers le format Bedrock JSON.
• Le client permet à l'application d'interagir avec le serveur en listant et en appelant des outils, facilitant ainsi l'intégration avec des modèles comme Claude.