Claude Code 2.x defers MCP tool schemas behind ToolSearch — tools are listed
but calling them by short name (e.g. fn_review_spec) returns "tool not found"
until ToolSearch loads the schema. Triage system prompts that say "call
fn_review_spec()" leave the model guessing whether to use the bare name or
the mcp__custom-tools__ form.
Append a system-prompt section listing every custom tool with its short and
MCP-prefixed names plus the ToolSearch + call protocol. Drives off the
Context.tools we now already thread through, so plain chats with no custom
tools get no addendum.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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