Catalog of this repo's measurement instruments, each with command, current baseline, and interpretation guide. Covers skill size and description budgets, orphan-ref and golden-principles scans, drift gates as signals, guard telemetry and maturity tiers, coverage pins, and the eval harness. Use when you say `measure this`, `read the drift signal`, `check skill budgets`, `guard maturity report`. Do NOT use to fix what you measure (use `ai-agents-debugging-playbook`) or for evidence standards (use `ai-agents-validation-and-qa`).
Install with Codex or Claude Copy this prompt, paste it into Codex, Claude, or another assistant, and let it review the skill page and install it for you.
A direct command skips the review prompt. Inspect the source before running it.
Catalog of this repo's measurement instruments, each with command, current baseline, and interpretation guide. Covers skill size and description budgets, orphan-ref and golden-principles scans, drift gates as signals, guard telemetry and maturity tiers, coverage pins, and the eval harness. Use when you say `measure this`, `read the drift signal`, `check skill budgets`, `guard maturity report`. Do NOT use to fix what you measure (use `ai-agents-debugging-playbook`) or for evidence standards (use `ai-agents-validation-and-qa`).
ai-agents Diagnostics Toolkit
Measure instead of eyeball. Every instrument below is a read-only command that turns a vague worry ("are skills getting bloated?", "did generation drift?") into a number you can compare against a baseline. The Instrument Index gives you, per instrument, the question it answers and the exact command; references/instrument-guides.md gives the healthy and unhealthy reading, the current repo baseline (as of 2026-07-29), and the trap that has already cost someone time.
Vocabulary, defined once: an "instrument" is a script whose output you read, not a gate you must pass. A "drift gate" is a CI check that fails when a generated tree stops matching its canonical source. "EVENT telemetry" is the one-line JSON a push guard prints to stderr when it runs. A "baseline" is the number the instrument reports on a clean checkout of main; you measure your delta against it.
Triggers
measure this
read the drift signal
check skill budgets
guard maturity report
interpret this scan output
Instrument Index
Instrument
Question it answers
Command (from repo root)
Description budget
How much standing context do skill descriptions cost?
uv run python ./scripts/skill_description_budget.py
Skill size
Which SKILL.md files exceed the 300-warn / 500-block line limits?
uv run python ./scripts/validation/skill_size.py
Orphan refs
Do specs, evals, and manifests reference entities that no longer exist?
uv run python "${COPILOT_PLUGIN_ROOT:-${CLAUDE_PLUGIN_ROOT:-.claude}}/skills/orphan-ref-validator/scripts/scan.py"
Golden principles
Where does the repo violate GP-001..GP-005 mechanical rules?
uv run python "${COPILOT_PLUGIN_ROOT:-${CLAUDE_PLUGIN_ROOT:-.claude}}/skills/golden-principles/scripts/scan_principles.py"
Agent drift
Do generated agent files match their templates?
uv run python build/generate_agents.py --validate
Mirror drift
Do the 7 generated mirror trees match .claude/ canonical sources?
uv run python build/scripts/build_all.py --check
Lib drift
Do .claude/lib/ copies match scripts/ canonical modules?
uv run python ./scripts/sync_plugin_lib.py --check
Guard maturity
Which push guards earn their keep?
uv run python "${COPILOT_PLUGIN_ROOT:-${CLAUDE_PLUGIN_ROOT:-.claude}}/skills/guard-maturity/scripts/run_report.py"
Coverage
Is changed code actually exercised by tests?
uv run pytest <tests> --cov=<module> --cov-branch
Eval A/B
Did a prompt or agent change alter behavior, measurably?
uv run python ./scripts/eval/eval-prompt-change.py --scenarios <file> --dry-run
Commit count
Am I approaching the 20-commit PR cap?
git rev-list --count HEAD ^origin/main
Process
Phase 1: Pick the instrument
Match the worry to the row in the Instrument Index. Two routing rules:
If you want to...
Go to
Fix the failure an instrument surfaced
ai-agents-debugging-playbook
Know what counts as test evidence
ai-agents-validation-and-qa
Prove a runtime hypothesis with a probe
ai-agents-empirical-probe-toolkit
Regenerate after a drift red
ai-agents-generation-and-release
Query agent JSONL event logs
observability skill (do not duplicate it)
Get adoption metrics from git history
metrics skill (collect_metrics.py)
Phase 2: Run it correctly
Run from the repo root. All commands above assume it.
Use uv run python, not bare python3, for anything that imports repo modules (PyYAML lives in the venv; bare python3 gives ModuleNotFoundError: No module named 'yaml').
All instruments here are read-only in the modes shown. build_all.py --check runs its generators and then restores the owned trees from a snapshot (issue #2440, build/scripts/build_all.py:1005-1033), so its log prints Mode: Generate and a nonzero Written: count even though nothing changes on disk. Confirm with git status --porcelain if suspicious, and see the trap in the Drift gates section of references/instrument-guides.md.
Read the exit code, not just the prose. It is the machine signal:
Exit code
Convention (ADR-035 / AGENTS.md)
Exceptions
0
Healthy or within limits
skill_size.py prints FAIL lines but exits 0 unless --ci
1
Logic finding (budget exceeded, CRITICAL_FAIL, over limit in --ci)
2
Config error (bad path, bad args) or staleness for build_all.py --check
10
Violations found
scan_principles.py only
Phase 3: Read the number against the baseline
Compare against the "Current baseline" entry in each guide in references/instrument-guides.md. The repo baseline is NOT all green: golden principles is red on main today (exit 10, 109 errors), and the description budget is over its 8000-token gate at ~10235 (exit 1 in gate mode). What matters for your change is the delta: your PR should add zero new findings, and should not grow a budget without saying so.
Phase 4: Act on the reading
Green and unchanged: move on. Red where the baseline was green: your change caused it; triage via ai-agents-debugging-playbook. Red where the baseline was already red: not yours to fix silently, but flag it (see-something-say-something) and keep your delta clean.
Instrument Guides
Per-instrument detail (the exact command variants, the current repo baseline as of 2026-07-29, the healthy and unhealthy readings, and the trap each instrument has already cost someone) lives in references/instrument-guides.md. Pick the instrument from the index above, then consult its section. That reference also carries the Current Baselines Summary snapshot.
Anti-Patterns
Anti-pattern
Why it burns you
Eyeballing ("the diff looks fine") instead of running the instrument
The 2025-12-15 drift inversion and PR #1887's 0/35 prevented-fix audit both started with confident eyeballs
Treating a red baseline as your failure, or silently "fixing" it repo-wide
Mass edits outside your scope; PR #908's scoped-lint lesson. Flag it, keep your delta clean
Quoting the chars/4 token estimate as an exact cost
It is a trend instrument, by design
Reading Mode: Generate in --check output as proof the gate wrote files
#2440 snapshot/restore makes it read-only; check git status --porcelain
Fixing scanner findings inside generated trees
Regenerated over on the next build; fix the .claude/ canonical source
--cov=<file path> or an uncalibrated --cov-fail-under pin
0% "Module never imported" (#2063) or a 63% false trip (#1963)
Running a paid eval without --dry-run and a written prediction first
Spend with no falsifiable claim; see ai-agents-research-methodology
Adding a detector or threshold without replaying it against recent real PRs
#1989 M4 shipped a threshold of 6 in a repo whose max was 4; it could never fire
Verification
Before citing any number from this toolkit in a PR, session log, or decision:
The command was run from repo root with uv run python and the exit code was captured, not just the prose output.
The reading was compared against the baselines in references/instrument-guides.md, and what you report is the DELTA your change introduces.
Any red you did not cause is flagged in your PR description, not silently fixed or silently ignored.
Volatile numbers you quote are date-stamped, the way this file stamps its own.
Provenance and Maintenance
Written 2026-07-02; every baseline in this skill re-measured 2026-07-29 by running each instrument on this checkout. Under the current squash-only policy, PR-branch SHAs do not land on main. One merge commit predates that policy (0f13c85ab, PR #1, 2025-12-13), so verify ancestry instead of assuming. Do not use git log to re-derive any of this.
uv run python ./scripts/skill_description_budget.py
Skill size FAIL list
uv run python ./scripts/validation/skill_size.py
Orphan-ref verdict and counts
uv run python "${COPILOT_PLUGIN_ROOT:-${CLAUDE_PLUGIN_ROOT:-.claude}}/skills/orphan-ref-validator/scripts/scan.py" (read last line)
Golden-principles totals
uv run python "${COPILOT_PLUGIN_ROOT:-${CLAUDE_PLUGIN_ROOT:-.claude}}/skills/golden-principles/scripts/scan_principles.py" (read last line, expect exit 10 while baseline is red)
When a baseline here goes stale (a red turns green or a number moves), update the table in the same PR that moved it, or file an issue pointing at this file.
