Writing Agent Briefs

An agent brief is a structured comment posted on a GitHub issue or PR when it moves to ready-for-agent. It is the authoritative specification that an AFK agent will work from. The original body and discussion are context: the agent brief is the contract.

The brief states what the agent should do, which stretches to both surfaces: for an issue, that's building the change from nothing; for a PR, it's what's left to do to the existing diff: finish it, close gaps, address review points. Same principles either way; the PR example below shows the difference.

Principles

Durability over precision

The issue may sit in ready-for-agent for days or weeks. The codebase will change in the meantime. Write the brief so it stays useful even as files are renamed, moved, or refactored.

• Do describe interfaces, types, and behavioral contracts
• Do name specific types, function signatures, or config shapes that the agent should look for or modify
• Don't reference file paths: they go stale
• Don't reference line numbers
• Don't assume the current implementation structure will remain the same

Behavioral, not procedural

Describe what the system should do, not how to implement it. The agent will explore the codebase fresh and make its own implementation decisions.

• Good: "The SkillConfig type should accept an optional schedule field of type CronExpression"
• Bad: "Open src/types/skill.ts and add a schedule field on line 42"
• Good: "When a user runs /triage with no arguments, they should see a summary of issues needing attention"
• Bad: "Add a switch statement in the main handler function"

Complete acceptance criteria

The agent needs to know when it's done. Every agent brief must have concrete, testable acceptance criteria. Each criterion should be independently verifiable.

• Good: "Running gh issue list --label needs-triage returns issues that have been through initial classification"
• Bad: "Triage should work correctly"

Explicit scope boundaries

State what is out of scope. This prevents the agent from gold-plating or making assumptions about adjacent features.

Template

## Agent Brief

**Category:** bug / enhancement
**Summary:** one-line description of what needs to happen

**Current behavior:**
Describe what happens now. For bugs, this is the broken behavior.
For enhancements, this is the status quo the feature builds on.

**Desired behavior:**
Describe what should happen after the agent's work is complete.
Be specific about edge cases and error conditions.

**Key interfaces:**
- `TypeName`: what needs to change and why
- `functionName()` return type: what it currently returns vs what it should return
- Config shape: any new configuration options needed

**Acceptance criteria:**
- [ ] Specific, testable criterion 1
- [ ] Specific, testable criterion 2
- [ ] Specific, testable criterion 3

**Out of scope:**
- Thing that should NOT be changed or addressed in this issue
- Adjacent feature that might seem related but is separate

Examples

Good agent brief (bug)

## Agent Brief

**Category:** bug
**Summary:** Skill description truncation drops mid-word, producing broken output

**Current behavior:**
When a skill description exceeds 1024 characters, it is truncated at exactly
1024 characters regardless of word boundaries. This produces descriptions
that end mid-word (e.g. "Use when the user wants to confi").

**Desired behavior:**
Truncation should break at the last word boundary before 1024 characters
and append "..." to indicate truncation.

**Key interfaces:**
- The `SkillMetadata` type's `description` field: no type change needed,
  but the validation/processing logic that populates it needs to respect
  word boundaries
- Any function that reads SKILL.md frontmatter and extracts the description

**Acceptance criteria:**
- [ ] Descriptions under 1024 chars are unchanged
- [ ] Descriptions over 1024 chars are truncated at the last word boundary
      before 1024 chars
- [ ] Truncated descriptions end with "..."
- [ ] The total length including "..." does not exceed 1024 chars

**Out of scope:**
- Changing the 1024 char limit itself
- Multi-line description support

Good agent brief (enhancement)

## Agent Brief

**Category:** enhancement
**Summary:** Add `.out-of-scope/` directory support for tracking rejected feature requests

**Current behavior:**
When a feature request is rejected, the issue is closed with a `wontfix` label
and a comment. There is no persistent record of the decision or reasoning.
Future similar requests require the maintainer to recall or search for the
prior discussion.

**Desired behavior:**
Rejected feature requests should be documented in `.out-of-scope/<concept>.md`
files that capture the decision, reasoning, and links to all issues that
requested the feature. When triaging new issues, these files should be
checked for matches.

**Key interfaces:**
- Markdown file format in `.out-of-scope/`: each file should have a
  `# Concept Name` heading, a `**Decision:**` line, a `**Reason:**` line,
  and a `**Prior requests:**` list with issue links
- The triage workflow should read all `.out-of-scope/*.md` files early
  and match incoming issues against them by concept similarity

**Acceptance criteria:**
- [ ] Closing a feature as wontfix creates/updates a file in `.out-of-scope/`
- [ ] The file includes the decision, reasoning, and link to the closed issue
- [ ] If a matching `.out-of-scope/` file already exists, the new issue is
      appended to its "Prior requests" list rather than creating a duplicate
- [ ] During triage, existing `.out-of-scope/` files are checked and surfaced
      when a new issue matches a prior rejection

**Out of scope:**
- Automated matching (human confirms the match)
- Reopening previously rejected features
- Bug reports (only enhancement rejections go to `.out-of-scope/`)

Good agent brief (PR)

For a PR, "Current behavior" describes the state of the diff, and the brief asks the agent to finish or fix it rather than build from scratch.

## Agent Brief

**Category:** enhancement
**Summary:** Finish the contributor's `--json` output flag for `triage list`

**Current behavior:**
The PR adds a `--json` flag that serializes the issue list to JSON. The happy
path works and the diff matches the project's command structure. Two gaps
remain: errors are still printed as human text (not JSON), and the new flag has
no test coverage.

**Desired behavior:**
With `--json`, all output (including errors) is well-formed JSON on stdout,
and the command's exit codes are unchanged. The existing human-readable output
is untouched when the flag is absent.

**Key interfaces:**
- The command's error path should emit `{ "error": string }` under `--json`
  instead of the plain-text error
- Reuse the existing serializer the PR already added; don't introduce a second

**Acceptance criteria:**
- [ ] `triage list --json` emits valid JSON for both success and error cases
- [ ] Exit codes match the non-JSON command
- [ ] A test covers the `--json` success output and one error case
- [ ] Default (non-JSON) output is byte-for-byte unchanged

**Out of scope:**
- Adding `--json` to any other command
- Changing the JSON shape of the success payload the PR already defined

Bad agent brief

## Agent Brief

**Summary:** Fix the triage bug

**What to do:**
The triage thing is broken. Look at the main file and fix it.
The function around line 150 has the issue.

**Files to change:**
- src/triage/handler.ts (line 150)
- src/types.ts (line 42)

This is bad because:

• No category
• Vague description ("the triage thing is broken")
• References file paths and line numbers that will go stale
• No acceptance criteria
• No scope boundaries
• No description of current vs desired behavior