Skill name+description pairs are preloaded into every session, costing ~6,200 tokens across 39 skills before any skill is invoked. The authoring rules mandated that growth: skill-author:104 and description-quality.md:21 both required padding, while skill-author:102 (the deflating rule) had no FAIL condition behind it. Gates (blocking, no baseline file): - description 250 chars SUGGESTION / 400 FAIL, measured on the folded YAML value - body-only 600 words SUGGESTION / 900 FAIL, independent of the unchanged whole-file 2770-word / 500-line spec backstop - every boundary-clause routing target must resolve to a real skill or agent; catches skill-improve, neuledge-context and gitea-labels - agents take the description gates but deliberately no body gate; a test pins that absence Vale: DescriptionOpener widened to ^This\b, new CompositionNote rule banning architecture notes from descriptions. 10 hits, 0 false positives. Kyberforge's own four skills retrofitted: descriptions 3,364 -> 938 chars (-72%), bodies 8,306 -> 2,487 words (-70%), all via the apm-workflow dispatch pattern. Fixes the skill-improve dangling route and the agent-author misroute to manual review. Also fixes a pre-existing false positive where any line-initial 'read ' was flagged as interactive input, which had already caused two scripts to be rewritten around it. Refs: ADR-0020
118 lines
6.1 KiB
Markdown
118 lines
6.1 KiB
Markdown
---
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source_keys:
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- agentskills-spec
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- agentskills-optimizing-descriptions
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---
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# Description Quality Reference
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Upstream source: agentskills.io — optimizing-descriptions, specification.
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House contract: ADR-0020, the context budget. The house contract is narrower than the spec
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rather than a reinterpretation of it: where both speak, both must be satisfied.
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## Why the description is the expensive part
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At startup an agent loads only the `name` and `description` of every installed skill. The body is
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never seen until the skill triggers. The description therefore carries the entire triggering
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burden **and** is paid for in every session, whether the skill fires or not.
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A second cost is less obvious and is a correctness hazard rather than a token cost: a description
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that summarises the workflow is a shortcut the agent takes *instead of* reading the body. A
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measured failure upstream — a description saying "code review between tasks" — produced one review
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where the body's flowchart specified two.
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## Step 0 — establish which contract applies
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Read the frontmatter before judging a single word.
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- **`disable-model-invocation: true`** — the skill is hand-invoked. Its description is never
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matched against user intent, so it is not a routing string. It carries **one plain human-facing
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sentence** stating what the skill does. Audit it for that and nothing else. Reporting a missing
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trigger clause, a missing boundary clause or absent indirect triggers on a hand-invoked skill is
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a wrong finding, not a strict one.
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- **No such flag** — the skill is model-invoked and the rest of this file applies.
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## The three-part shape
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A model-invoked description carries exactly three things:
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1. **Trigger clause.** When to invoke, phrased imperatively: `Use when ...`. Not `This skill ...` —
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the agent is deciding whether to act, not reading a catalogue entry.
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2. **At most one capability clause.** What it does, in one clause. Never an enumeration.
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3. **Boundary clause.** Compressed form: `Not <thing> -> <skill-name>.` The target must resolve to
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a real skill directory or agent file in the authoring source; `validate.sh` checks that
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deterministically and a dangling target already surfaces as a Structure FAIL.
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Everything else belongs in the body or in `README.md`.
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## Indirect triggers — conditional, never blanket
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Add "even if the user doesn't say X" **only where the user's natural phrasing genuinely omits the
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domain word.** True for the `gitea-*` family: people say "create an issue", not "create a Gitea
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issue". False for `git-commits`: nobody asks for a commit without saying commit. A blanket
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indirect-trigger clause on a skill whose domain word is unavoidable is padding charged to every
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session.
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## Near-miss exclusions
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Add a boundary clause only where a sibling skill could plausibly steal the activation. Use strong
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near-misses — queries that share keywords but need something different — not weak ones ("write a
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fibonacci function"). One boundary clause per genuine near-miss; a list of four is enumeration
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wearing a boundary's clothes.
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## Before / after
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```yaml
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# FAIL — enumeration first, mechanics as the opener, a blanket indirect trigger,
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# and 300+ characters of it preloaded into every session forever.
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description: >
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Analyze CSV and tabular data files — compute summary statistics, add derived
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columns, generate charts, and clean messy data. Use when the user has a CSV,
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TSV, or Excel file and wants to explore, transform, or visualize the data,
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even if they don't explicitly mention "CSV" or "analysis."
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# PASS — trigger, one capability clause, boundary. The four verbs the FAIL
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# version enumerates are the body's job; the router cannot act on them.
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description: >
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Use when the user has a CSV, TSV, or Excel file and wants it explored,
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transformed, or charted. Not schema design -> data-model.
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```
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(`data-model` is illustrative. In a real description the target has to resolve.)
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## Auditing guidance
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Flag as FAIL if:
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- **Over 400 characters.** Measured on the folded YAML value, not the raw source lines.
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`validate.sh` reports the number; do not re-derive it, but do point the Fix at what to cut.
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- **Internal mechanics appear in the description.** Any of:
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- capability enumeration or a feature list;
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- output-format detail ("Produces a compact findings report with Why and Fix per finding");
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- composition or architecture notes ("composes X rather than duplicating Y", "a cross-cutting
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shared skill", "the human-facing entry point", "replaces the old flat invocation");
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- implementation detail ("self-validates via a bundled deterministic script").
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None of it can change a routing decision and all of it is preloaded.
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`Kyberforge.CompositionNote` catches the common phrasings deterministically; the rest is
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judgment. This is the rule that deflates a description, so apply it before reaching for length.
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- **The same trigger stated twice in two registers** — a verb list, then the same verbs re-quoted
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as user phrasings, usually in the same order. One register, whichever routes better.
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- **Descriptive rather than imperative phrasing** (`This skill ...`, `This is the ...`).
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`Kyberforge.DescriptionOpener` catches any opener matching `^This`.
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- **Vague capabilities** ("helps with APIs" where "parses and validates OpenAPI specs" was
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available). `Kyberforge.VagueWording` catches the known filler; imprecision outside that list is
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judgment.
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- **A boundary clause naming a target that does not resolve** to a real skill directory or agent
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file in the authoring source. `validate.sh` reports the unresolved name.
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- **Trigger-list, boundary or indirect-trigger content on a hand-invoked skill** — see Step 0.
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- **Over 1024 characters** — the agentskills.io specification ceiling, unchanged and independent
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of the 400-character house ceiling above.
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Flag as SUGGESTION if:
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- **Over 250 characters** but at or under 400. This tier is what moves the corpus average; the FAIL
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tier only stops outliers. Report it rather than treating a 399-character description as clean.
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- A near-miss exclusion is present but targets a weak near-miss.
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- An indirect trigger is present and warranted but could name the omitted phrasing more precisely.
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