Anthropic's Tool Search reveals MCP's context overhead was degrading model accuracy by up to 25 points

Short summary

Anthropic's Tool Search feature (launched with Claude Opus 4.5) lets tools be lazy-loaded into context only when needed, boosting accuracy from 49% to 74% on Opus 4 and from 79.5% to 88.1% on Opus 4.5. The author argues this is an implicit admission that MCP's upfront schema loading was degrading model performance by up to 25 percentage points. Meanwhile, the community tool mcporter takes the opposite approach, converting MCP servers to plain code to eliminate protocol overhead entirely.

• •Tool Search lazy-loads MCP schemas, improving accuracy up to 25 percentage points
• •Anthropic implicitly admits MCP's context cost was a real problem
• •mcporter offers an alternative: convert MCP servers to plain code, zero protocol overhead

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