How do you implement a call tool function in an MCP client?

The call tool function executes a specific tool on the MCP server. Your function takes two arguments: the tool name and the input parameters that Claude provided. You pass both to the session's call tool method, await the result, and return it back to your caller. This single function is what powers every tool execution Claude triggers. Because the session handles the actual message exchange with the server, your code stays small and focused. The whole client implementation is essentially just a constructor, a list tools method, and a call tool method, plus the lifecycle code that opens and closes the session.