Claude Code handles tool schemas differently depending on the subagent model. Sonnet and Opus get lazy loading: tools are listed by name only, and loaded on demand via ToolSearch. Haiku doesn’t get this mechanism at all. For Haiku, every MCP and non-MCP tool schema is eagerly dumped into context before the model even runs. A trivial Explore subagent saying Hi on Haiku will just kill your quota if you have too many tools/mcps available. Explore(Say hi (Haiku Explore)) Haiku 4.5 ⎿ Done (0 tool uses · 41.6k tokens · 1s) https://github.com/anthropics/claude-code/issues/37793 https://github.com/anthropics/claude-code/issues/37793 submitted by /u/qnoxo
Originally posted by u/qnoxo on r/ClaudeCode
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