skillprune

Every agent skill you install puts its name and description into the system prompt on every turn, forever. Installing is one click; nothing tells you what to remove.

The OSS ecosystem has solved discovery and install several times over — SkillDock (519★), skillfish (315★), skilld (308★). The other half of the loop is empty: every audit/eval/conflict tool on GitHub sits at 1–14 stars.

skillprune is that other half. It reads your real transcript history and tells you what to turn off.

uvx skillprune                   # run it, install nothing
pipx install skillprune          # or keep it around

skillprune                       # report
skillprune --prune               # act on it, reversibly
skillprune --json                # + skillprune.json
skillprune --selfcheck           # the guards below, as assertions

No install needed either way — it is one stdlib-only file, so python3 skillprune.py works straight from a clone.

Example, on a real 291-skill install:

  171 loaded    35 fired    123 dead    13 too new to judge
  125 more sit on disk, not loaded by any plugin — those cost nothing

  ████████████████████░░░░░░░░  72% of your skill surface has never fired

  ~15,673 tokens in every system prompt, for skills that have never fired
  71% of the ~22,169 tokens your skills cost you per turn

Removing what it finds

skillprune --prune prints a plan, asks once, and applies it. Two levers, because they are two different things:

• Plugins where not one skill has ever fired → claude plugin disable. Reversible with enable. A plugin with even one live skill is never offered.
• Personal skills in ~/.claude/skills/ → moved, never deleted, to ~/.claude/.skillprune-trash/<timestamp>/, next to a generated restore.sh that puts every one of them back.

There is no per-skill disable for plugin skills — the plugin is the unit the tool manages, so that is the unit offered.

How it decides

Nothing leaves the machine. No dependencies beyond the standard library.

Where it deliberately errs

A tool that says delete this has one unacceptable failure: naming something you actually use. Five guards, each pinned by an assertion in --selfcheck:

• Slash commands count. A skill invoked only as /foo never produces a Skill tool call. Counting just the tool call marks it dead.
• Hooks count. A plugin shipping a SessionStart hook runs every session with an invocation count of zero. Those are held back, never auto-disabled.
• Bare-name matching. Transcripts log <plugin>:<skill>, and that prefix often disagrees with the marketplace directory the skill was found in. Two plugins sharing a skill name will cross-credit — that errs toward in use, the only safe direction here.
• On disk is not loaded. A marketplace you added and a plugin you later uninstalled both leave complete SKILL.md trees behind, and neither costs a single prompt token. Only what installed_plugins.json actually points at is counted. Skipping this inflated the count on the author's own machine from a true 171 to 291.
• 14-day grace. Something installed yesterday hasn't had its chance. Tune GRACE_DAYS; skills under it are reported separately, never as dead.

Collision detection is Jaccard overlap on description word-sets (COLLIDE, default 0.35) — crude next to embeddings, but it needs no model and no network.

MIT.