Implementing a client

MCP Client Study Notes

**I. Core Concepts & Purpose**

• Dual System: The project operates by implementing both a client and a server, allowing the developer to see both sides of the interaction.
• Client Role: The MCP client acts as an interface that exposes functionality implemented on the MCP server to the rest of the codebase.
• Functionality: The client allows the application to:
• Retrieve server data (e. g. , list tools, list prompts, get prompt).
• Execute server functions (e. g. , call a specific tool).

**II. Client Structure and Design**

• Client Composition: The MCP client is a single class that wraps a client session.
• Client Session: This session is the actual connection to the external MCP server (part of the MCP Python SDK).
• Resource Management: The client class is primarily designed to manage the lifecycle of the client session, ensuring proper resource cleanup when the program closes or the connection is no longer needed.
• Design Pattern: It is standard practice to wrap the raw client session within a larger management class (the MCP client class) to simplify resource handling.

**III. Key Functionality Implementation**

• list_tools Function:
• Accesses the self. session (the server connection).
• Calls the built-in function list_tools.
• Returns the resulting list of all tools defined by the server.
• call_tool Function:
• Accesses the self. session.
• Attempts to execute a specific tool on the server.
• Requires the tool_name and the tool_input (parameters provided by the LLM/Claude).

**IV. Workflow Integration**

• Tool Discovery: The client enables the application to retrieve tool definitions (including descriptions and input schemas) from the server.
• LLM Interaction: Once tools are defined and callable via the client, the main application can prompt the LLM (e. g. , Claude) to decide when and how to use those tools (e. g. , asking Claude to read a document, which triggers the read_document tool).

Takeaways

• The MCP client acts as an interface, exposing server functionality (data retrieval and function execution) to the application.
• The client class wraps a client session, primarily managing the connection lifecycle and ensuring proper resource cleanup.
• It enables tool discovery by allowing the application to retrieve definitions and schemas for all server-defined tools.
• The call_tool function executes specific server functions, requiring both the tool name and the necessary input parameters.
• The overall workflow allows the LLM to interact with the client to decide when and how to utilize available tools.