Chapter C58 · Interactive Course
MCP and its neighboring ideas
APIs, tool calling, skills, retrieval, agent delegation and packages.
Core Learning Concept
Match each need to the appropriate layer: procedure, model tool interface, MCP connection, retrieval arrangement, agent delegation, or plugin packaging. These pieces can work together. Explain the role each contributes rather than treating similar marketing terms as competing names for the same capability.
What You’ll Learn in This Chapter
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MCP can wrap an existing API
Locate the underlying service behind an MCP server.
An MCP server can adapt an existing API into MCP tools or resources. The underlying service still performs its own work and enforces its own rules. Trace beyond the protocol boundary to identify where data is stored and actions happen. The adapter does not automatically replace the service’s API.
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Function calling and MCP occupy different layers
Separate a model's structured action proposal from a server protocol.
Model function or tool calling describes how a model requests operations through its host. MCP describes communication between a client and server exposing capabilities. A host can translate between these layers. They can be used together, but supporting model tool calls does not automatically mean an MCP integration is configured.
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A skill teaches a procedure
Contrast reusable guidance with connected capability.
A skill supplies reusable know-how: instructions and resources for performing a task. A connected tool supplies an executable capability. A procedure may require tools that are not available, and a tool may be used poorly without useful guidance. Diagnose the actual missing piece rather than assuming either one guarantees success.
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RAG supplies evidence
Distinguish retrieval-augmented answering from the protocol carrying retrieval.
RAG is an arrangement that retrieves material and supplies it to generation. MCP can provide access to a retrieval capability or its sources, but is not required for RAG. Conversely, an MCP connection may perform tasks unrelated to retrieval. Describe the mechanism and the integration boundary separately.
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A2A connects agent task interfaces
Recognize delegation between separately operated agents.
Agent-to-agent protocols coordinate tasks, state, and artifacts across independent agent systems. While MCP connects applications to server tools and resources, A2A protocols delegate complete autonomous multi-turn workflows across organizational agent boundaries.
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A plugin can package several pieces
Map a skill, MCP config and hook into a host package.
A plugin can package several extension types, such as a skill, a connector, and event handlers. Portability depends on the host’s supported packaging and features. Inspect the bundle’s contents and dependencies rather than assuming that moving a folder makes every included capability work in another product.
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Pick the layer
For five fictional needs, choose guidance, model tool calling, service API, MCP integration or agent delegation, allowing sensible combinations.