---
source_keys:
  - context7-websites-code-claude
  - claude-code-subagents-docs
  - context7-github-en-copilot
  - github-custom-agents-configuration
---

# Agent Description Quality Reference

Upstream source: Claude Code subagent reference, GitHub Copilot custom-agents configuration.
House contract: ADR-0020, the context budget. The house contract is narrower than either
platform's schema rather than a reinterpretation of it: where both speak, both must be satisfied.

## Why the description is the expensive part

At startup an agent loads only the `name` and `description` of every installed skill and agent.
The body is never seen until the agent is invoked. The description therefore carries the entire
triggering burden **and** is paid for in every session, whether the agent fires or not.

A second cost is less obvious and is a correctness hazard rather than a token cost: a description
that summarises the workflow is a shortcut the caller takes *instead of* reading the body. A
measured failure upstream — a description saying "code review between tasks" — produced one review
where the body's flowchart specified two.

## Step 0 — establish which contract applies

Read the frontmatter before judging a single word.

- **`disable-model-invocation: true` or `user-invocable: false`** — the agent is hand-invoked. Its
  description is never matched against user intent, so it is not a routing string. It carries **one
  plain human-facing sentence** stating what the agent does. Audit it for that and nothing else.
  Reporting a missing trigger clause, a missing boundary clause or absent indirect triggers on a
  hand-invoked agent is a wrong finding, not a strict one. Both fields are Copilot-only and neither
  is on the vendor-neutral APM allowlist, so this case arises in a Copilot `.agent.md` at
  project/user scope and nowhere else. Its Claude Code counterpart has no equivalent field and stays
  model-invoked, so the two halves of the pair carrying differently shaped descriptions is expected
  there rather than a pair-consistency finding.
- **No such flag** — the agent is model-invoked and the rest of this file applies.

## The three-part shape

A model-invoked description carries exactly three things:

1. **Trigger clause.** When to invoke, phrased imperatively: `Use when ...`. Not `This agent ...` —
   the caller is deciding whether to act, not reading a catalogue entry.
2. **At most one capability clause.** What it does, in one clause. Never an enumeration.
3. **Boundary clause.** Compressed form: `Not <thing> -> <skill-name>.` The target must resolve to
   a real skill directory or agent file in the authoring source.

Everything else belongs in the body or in the plugin's `README.md`.

## Indirect triggers — conditional, never blanket

Add "even if the user doesn't say X" **only where the user's natural phrasing genuinely omits the
domain word.** True for the `gitea-*` family: people say "create an issue", not "create a Gitea
issue". False for `git-commits`: nobody asks for a commit without saying commit. A blanket
indirect-trigger clause on an agent whose domain word is unavoidable is padding charged to every
session.

## Near-miss exclusions

Add a boundary clause only where a sibling skill or agent could plausibly steal the activation. Use
strong near-misses — queries that share keywords but need something different — not weak ones. One
boundary clause per genuine near-miss; a list of four is enumeration wearing a boundary's clothes.

## Before / after

```yaml
# FAIL — a noun-phrase opener rather than a trigger, capability enumeration in
# place of one capability clause, and no boundary clause at all, preloaded into
# every session forever. (The live git-orchestrate description, 254 chars.)
description: Orchestrates git workflow operations for other agents. Invoke when a
  caller needs a multi-step or destructive git operation (rebase, force-push, branch
  deletion) coordinated across domain skills with safety gates, session context, and
  structured results.

# PASS — trigger, one capability clause, boundary. The operation list and the
# safety-gate mechanics are the body's job; the router cannot act on them.
description: >
  Use when an agent caller needs a multi-step or destructive git operation
  dispatched and safety-gated. Not conversational git help -> git-workflow.
```

## Where the criteria live

Every FAIL and SUGGESTION criterion for this dimension is in `references/finding-criteria.md`,
which Step 3 reads on every run. This file is the reasoning behind them, loaded only when that file
puts the description dimension in play.