Analyzing Collaboration Mechanisms of Tool, Function Calling, MCP, and Skill

On November 11, 2026, a Juejin article titled "Tool, Function Calling, MCP, and Skill Collaboration Mechanism Explained" set out to clarify how Tool, Function Calling, MCP, and Skill work together inside an AI agent. The piece follows a single concrete action, reading a product guide, and threads the four concepts through it to show how each one contributes. In that framing, the tool is the capability that gets used, Function Calling is the way the model expresses the request to invoke it, MCP serves as the access protocol that brings the tool into the agent's environment, and Skill represents the working method that shapes how the task is carried out. Rather than stopping at abstract definitions, the article walks through the full execution path and points readers to public code where the complete process can be observed. Along the way it highlights how a tool's declared capability, the model's call expression, the protocol-level connection, and the higher-level working method fit together to support a single run. In doing so it offers a working mental model for readers who want to understand how these pieces compose in practice.