brain_index is auto-called after every write, and its own description said so. A verb surfaced to callers that callers should never call is cognitive load with no decision behind it — ADR-0012 rule 4. Removed from tools/list only. The dispatch case stays, so maintenance can still rebuild a Map of Content by hand: de-surfacing hides the verb, not the operation. A test pins both halves, since removing the descriptor and removing the capability look identical from the tool list. Nothing called it directly — grepped the skills, specs and docs. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01BeAp5LTscnz2W7Ubt4eJ6m