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Part 6: Context as Tool Definitions — MCP
NOTE
Context consumed by tools.
As more MCP servers are connected, the context available for actual work decreases.
MCP is both a representative example in Claude Code and an open way to connect external tools. That tool definitions are a fixed cost on Context is not product-specific.
Why This Matters
When you connect an MCP server, tool definitions (name, parameter schema, description) are injected into the context window every turn. When multiple MCPs are connected, tool definitions alone can consume 20K+ tokens, drastically reducing the context available for actual work.
→ Why: Which Structural Problems Does This Address?
- Context Rot: The constant consumption of tool definitions puts pressure on context
- Knowledge Boundary: External knowledge retrieval via MCP reduces dependency on the LLM's internal knowledge
TIP
MCP grounds the LLM in external-world facts (APIs, databases, wikis). For code-world facts (symbols, types, references in the repository), see Part 9: Code Intelligence. Together they form the two pillars of factual grounding.
Documentation in This Part
| Document | Content |
|---|---|
| MCP Context Cost | The reality of how many tokens tool definitions consume |
| Tool Search / Deferred Loading | Lazy loading automatically enabled above 10% |
Previous: Part 5: On-Demand Context