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MCP Schema Tax: GitHub MCP Server Injects ~55,000 Tokens Before Your First Message
Each MCP tool definition consumes 550–1,400 tokens of context; the official GitHub MCP server exposes 93 tools, injecting roughly 55,000 tokens into every conversation before any user input. Perplexity CTO Denis Yarats stated that MCP tool schema overhead consumes up to 72% of available context window space at scale. A formal protocol change proposal (SEP-1576) is open in the MCP GitHub repo proposing schema redundancy reduction and dynamic tool selection as fixes — validating the MCP token overhead problem at the protocol level.
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