✨ Descriptio Reducio

"The router stops reading at 1,535 characters. Your masterpiece dies at 1,536."

Two facts about routing, both easy to forget: the router reads only the description: frontmatter, never the body — and listings truncate. In harnesses with a listing cap (around 1,500 characters in one measured setting; measure yours, the number is not a constant), everything past the cliff is invisible. Authors write descriptions front-loaded with capabilities and append the disambiguation ("NOT for: X → other-agent") last — exactly the part that falls off.

What to scan

Every description: in .claude/skills/*/SKILL.md, .claude/agents/*.md, plugin skills and agents, and any harness config that sets a listing cap.

Anti-patterns to find

1. Past the cliff. Description length exceeds the listing cap.

   Measure the cap from inside a session, not from this file. The listing is injected into the model's system prompt and never displayed, so "render the listing" is not something a user can do — but the agent running this pass can read its own listing. Procedure:

   a. Find the longest description in the repo: for f in .claude/skills/*/SKILL.md .claude/agents/*.md; do awk '/^description:/{print length($0)-13, FILENAME}' "$f"; done | sort -rn | head b. Ask the running agent to quote that description back verbatim from its own listing, and diff it against the file. Where the quote stops is the cap. c. If nothing in the repo is long enough to truncate, the cap is unmeasurable here: this class has no instances, and the pass grades ? (could not verify), not O. Do not substitute a number measured on another harness.

2. NOT-for clauses last. Disambiguation after the cliff — the router sees only the capabilities, so near-miss tasks route wrong. This is the highest-impact class: a truncated NOT-for is a routing defect, not a style issue.
3. Body-only disambiguation. The routing rule lives in the agent's body ("do not use this for X") where no router ever reads it.
4. Keyword stuffing. Fifty comma-separated trigger phrases; the description becomes noise and matches everything weakly.
5. Twin descriptions. Two skills/agents whose descriptions overlap enough that routing between them is a coin flip — the distinction exists only in the bodies.
6. Description restating the body. Procedure detail in the description (steps, flags, internal paths) that costs length without aiding routing.

Fix prescriptions

Ordering template

<What it does, one line>. Use for <top trigger phrases>. <Key constraint/behavior>.
NOT for: <adjacent-task> (→ <other-skill>), <adjacent-task> (→ <other-skill>).

Bounds

• If legilimens-anthropica ran this session, prefer its measured numbers over the ones in this file. This file is a snapshot; that pass is the current reading.
• Scope: the description: frontmatter of skills and agents, plus any harness config that sets a listing cap. Not skill bodies, except to note where a routing clause is stranded in one.
• Cap: measure every description (that is cheap and complete); cap the rewrites proposed at 15, highest routing impact first.
• Done when every description has been measured once against the cliff — or when the cap has been established as unmeasurable here, which is a ?, not a pass.
• Quote once, at read time; mark anything you cannot re-confirm UNVERIFIED rather than re-reading to check yourself.
• See skills/opus-pocus/references/casting-safety.md for the full rules.

Report format

Table: name · length · over-cliff? (by how much) · what falls off · rewrite proposed? Then each rewrite in full. Lead with the count of routing defects (class 1–3) vs style issues (4–6). SCANNED NOTHING if no skills or agents exist, grading N/A.