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An MCP server owns an assistant-facing protocol surface. It exposes tools, prompts, and resources through MCP. MCP servers exist because assistants need a protocol surface that is not the same as a user-facing app route. MCP describes capabilities an assistant can inspect and call.

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Characteristics

  • Tools expose actions.
  • Prompts expose reusable instructions.
  • Resources expose readable context.
  • Transport defines how the assistant connects.
  • Auth decides which clients can use the server.

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Boundary

MCP describes capabilities for assistants. App routes describe entry points for users and HTTP clients. Use an MCP server when an assistant needs to inspect or operate on a project through a protocol. MCP is not the same as AG-UI or REST. AG-UI streams agent output to app clients. MCP exposes tools, prompts, and resources to assistants.

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Wrong fit

Do not use MCP as the public API for normal app users. Use app routes or API routes for user-facing HTTP entry points. For implementation steps, see MCP server.