MCP — Tool context

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NOTE

Model Context Protocol (MCP) servers expose external services as tools the LLM can call. Tool definitions themselves consume context — design and discovery matters.

How it works

• Every connected MCP tool ships its name, description, and schema into context.
• Tool Search (deferred tools) lets the LLM fetch a tool's schema only when needed, keeping the default context lean.
• MCP is the primary path for grounding — pulling fresh facts from authoritative sources.

Related chapters

• Part 6 — Tool Context (overview)
• MCP Context Cost
• Tool Search
• Configuration Reference

Structural problems it addresses

• Hallucination — MCP grounds answers in real data.
• Knowledge Boundary — bypass the training cutoff with live tools.
• Context Rot — too many tool schemas defeats the purpose; Tool Search fixes this.

See also

• Topic: Skills & Agents — for self-contained capabilities (vs. external services).
• Topic: Plugins — for distributing bundles that include MCP servers.
• Feature Index