SecondBrain/reference/claude-code-tool-schema-costs-and-yagni-deny.md

summary	tags	scope	type	source	date	last_updated
Claude Code's non-deferred built-in tool schemas cost ~18k tokens/session; the Workflow schema alone is ~6k, and a permissions.deny block in settings.json removes unused tools' schemas entirely (measured −6.5k for four never-used tools).	type/reference tool/claude-code	global	reference	cc-os docs/plans/b2-profile-overlays.md (follow-on section, 2026-07-08)	2026-07-08	2026-07-08

Claude Code tool schemas: where the ~18k goes, and the YAGNI deny lever

Measured 2026-07-08 (headless haiku, --output-format json usage totals).

• The ~29k empty-dir context floor = ~6.3k system-prompt text + ~18k built-in tool schemas + ~4.8k user stack. ToolSearch deferral only covers the optional tier (Cron, LSP, NotebookEdit, Monitor, web tools…) — core schemas ship every request.
• Workflow's schema alone is ~6k tokens (−5,982 when disallowed) — about the size of the entire system-prompt text.
• "permissions": {"deny": ["Workflow", ...]} in ~/.claude/settings.json removes the denied tools' schemas from context, identical to --disallowedTools (22,532 vs 22,536 measured) — so a global deny needs no wrapper or flags.
• Ground truth for "which tools do I actually use": count tool_use names across ~/.claude/projects/**/*.jsonl transcripts. Five weeks of data (2026-06→07) showed zero-or-one lifetime calls to Workflow, Artifact, SendUserFile, ReportFindings → denied globally (−6.5k/session). Revert by removing the deny entry if Workflow ("ultracode" multi-agent orchestration) is ever wanted.

Related: claude-code-setting-sources-silent-plugin-drop, cc-os-hub