Agent skill

Discover Acs

by swingerman in swingerman/engineer

A skill your agent uses when a Ready feature needs its acceptance criteria discovered before specs are written.

MITAuto-check passedProduct & Project Management

Install Discover Acs

skills CLI
$ npx skills add swingerman/engineer --skill discover-acs -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install swingerman/engineer discover-acs --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/swingerman/engineer.git skills-src && mkdir -p .claude/skills && cp -r skills-src/engineer/skills/discover-acs .claude/skills/discover-acs && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
discover-acs
GitHub stars
154
Token cost
~2.2k tokens
SKILL.md length
1,065 words
Files
1
Skills in repo
27
Repo updated
First seen
Licence
MIT

At a glance

A skill your agent uses when a Ready feature needs its acceptance criteria discovered before specs are written.

  • Works in 9 steps: Resolve + validate — resolve the… → Load — feature.md, CHARTER.md,… → Discover the ACs → …
  • A Ready feature needs its acceptance criteria discovered before specs are written
  • SKILL.md covers When to use, Workflow, Handoff and References
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Discover Acs is an agent skill from swingerman/engineer. Use when a Ready feature needs its acceptance criteria discovered before specs are written. Triggers — "/engineer.discover-acs", "/engineer.acceptance-criteria", "discover ACs", "what must this feature do", "figure out acceptance criteria".

Its SKILL.md is about 2.2k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Product & Project Management, covering User stories. The repository describes itself as: Disciplined Agentic Engineering — a methodology kit for Claude Code: acceptance-test-first specs, explicit checkpoints, and autonomy you can actually leave running. The engineer… The licence is MIT.

When your agent uses it

  • A Ready feature needs its acceptance criteria discovered before specs are written
  • — /engineer.discover-acs
  • /engineer.acceptance-criteria
  • What must this feature do

Example prompts

  • “/engineer.discover-acs”
  • “/engineer.acceptance-criteria”
  • “discover ACs”
  • “/discover-acs”

Workflow steps

9 steps, taken from the first numbered list in SKILL.md.

  1. Resolve + validate — resolve the methodology root + manifest via ${CLAUDE_PLUGIN_ROOT}/scripts/dae_resolve.py (see…
  2. Load — feature.md, CHARTER.md, manifest.yml, prior handoffs/. Reverse-engineer mode: also load the existing spec / design doc / relevant…
  3. Discover the ACs
  4. Enforce domain language — when implementation leaks in ("returns 401", "the endpoint", table/class names), soft-warn and rephrase to the…
  5. Handle scope drift — if a behavior surfaces outside feature.md's outcome, offer three options: broaden feature.md, drop as out-of-scope…
  6. Coverage check — before writing, report ACs captured + which passes were covered; if a pass was skipped, prompt once.
  7. Write acs.md — YAML frontmatter (ac_count, high_priority_count, discovered) + numbered ## AC-N: sections, each with Priority, Type, and a…
  8. Review panel — dispatch the standing adviser + advocate pair against acs.md per ${CLAUDE_PLUGIN_ROOT}/references/review-panel.md. This is…
  9. Handoff — emit a summary.

What it can do on your machine

Read from SKILL.md and the folder at commit 32947eb. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Links to these hosts (documentation or services it may open):

    • notion.so

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Discover Acs loads about 2.2k tokens when it runs. Until then it costs about 63 tokens; SKILL.md has 1,065 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~63
When it runs · the whole SKILL.md, loaded when a task matches
~2.2k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from swingerman/engineer at commit 32947eb, republished under its MIT licence (© swingerman). 1,065 words, ~2,232 tokens.

Download SKILL.mdSave it as .claude/skills/discover-acs/SKILL.md (or your agent's skills folder).
name
discover-acs
description
Use when a Ready feature needs its acceptance criteria discovered before specs are written. Triggers — "/engineer.discover-acs", "/engineer.acceptance-criteria", "discover ACs", "what must this feature do", "figure out acceptance criteria".

discover-acs

Discover a feature's acceptance criteria — Checkpoint 2. ACs are decisions about what behaviors must work, in domain language. They precede the Given/When/Then formalization that atdd:atdd produces.

Separating AC discovery (divergent decisions) from spec formalization (convergent encoding) is what protects domain language from leaking into implementation language.

When to use

On a feature with autonomy_level set and status of ready (greenfield) or in-progress/done (onboarded existing work). Produces acs.md.

Two modes:

  • Greenfield — status: ready, no existing spec. Discover ACs from scratch via the four-pass interview.
  • Reverse-engineer — onboarded feature (in-progress/done) that already has a spec (a Speckit spec.md, a design doc, shipped code). Extract candidate ACs from the existing material, then interview only for the gaps it leaves.

Not for: a parked feature (discuss to promote first); a feature that already has a complete acs.md (feature-edit); producing Given/When/Then specs (atdd:atdd); deciding whether to build the feature (discuss).

Workflow

Step 0 — Entry gate. Before starting, verify the prior checkpoint is complete: run ${CLAUDE_PLUGIN_ROOT}/scripts/dae_handoff.py <feature-dir> --through 1.5. On a non-zero exit, stop and surface the gap to the human — do not proceed.

Verify branch hygiene: run ${CLAUDE_PLUGIN_ROOT}/scripts/dae_branch.py <feature-dir>. On a non-zero exit, stop and surface the message to the human — switch branches and re-invoke. The check honors the git.manual: true manifest opt-out.

After the gate passes, show the pipeline breadcrumb: run ${CLAUDE_PLUGIN_ROOT}/scripts/dae_progress.py <feature-dir> and present its output to the human — it shows where this checkpoint sits in the DAE pipeline. The breadcrumb is advisory: a non-zero exit or a missing progress.md never blocks the skill. Then create one TodoWrite todo per workflow step below. See ${CLAUDE_PLUGIN_ROOT}/references/progress-indicator.md.

  1. Resolve + validate — resolve the methodology root + manifest via ${CLAUDE_PLUGIN_ROOT}/scripts/dae_resolve.py (see references/resolving.md); locate the feature. Reject if not found, if status: parked (→ discuss to promote first), or if acs.md already exists with content. Pick the mode: existing spec/code present → reverse-engineer; else → greenfield.

  2. Load — feature.md, CHARTER.md, manifest.yml, prior handoffs/. Reverse-engineer mode: also load the existing spec / design doc / relevant code. For code lookup in reverse-engineer mode (surveying what exists, tracing what calls what), prefer LSP workspace-symbols / find-references when an LSP MCP capability is available; fall back to grep + Read otherwise. See ${CLAUDE_PLUGIN_ROOT}/references/code-lookup.md.

  3. Discover the ACs:

    • Greenfield — interview in four passes, one question per turn, coverage prompts per pass.
    • Reverse-engineer — extract candidate ACs from the existing material, organized by the four passes; then interview only for genuine gaps the material leaves undecided. Gap questions may be batched (e.g. one AskUserQuestion with up to 4) rather than one-per-turn — the existing material already carries the bulk.

    The four passes:

    • Happy path — the core journey, every behavior when all goes right
    • Edge cases — empty / extreme / boundary / concurrency / partial state
    • Errors & security — missing/malformed input, authorization, external failure, abuse
    • Cross-cutting — audit, observability, idempotency, data lifecycle, performance

    3b. Domain coverage checklists (MANDATORY pass). After the four interview passes, scan feature.md's outcome and scope for surface signals and consult any matching checklist in ${CLAUDE_PLUGIN_ROOT}/references/ac-coverage/:

    Signal phrase / keywordChecklist file
    public web page, site, marketing, HTML outputweb-seo.md
    login, OAuth, auth, session, token, SSOauth-oauth.md
    deploy, staging, production, infra, hosting, CI/CDdeploy-model.md
    UI component / page targeting humansaccessibility.md (when written)
    schema change, data backfill, migration, rename columndata-migration.md (when written)

    For each matched checklist: present its items as a single batched AskUserQuestion (multi-select) with the file's content as the option list. The human ticks "yes, this matters" / "no, out of scope" per item. Each ticked item becomes an AC candidate in Step 6/7. The checklists do not auto-create ACs without confirmation. image-titler shipped without a default og:image AC because nothing prompted the question — these checklists fix that class of gap.

  4. Enforce domain language — when implementation leaks in ("returns 401", "the endpoint", table/class names), soft-warn and rephrase to the user-observable behavior; user confirms. Don't block — educate.

  5. Handle scope drift — if a behavior surfaces outside feature.md's outcome, offer three options: broaden feature.md, drop as out-of-scope, or park a separate discuss. User picks.

  6. Coverage check — before writing, report ACs captured + which passes were covered; if a pass was skipped, prompt once.

  7. Write acs.md — YAML frontmatter (ac_count, high_priority_count, discovered) + numbered ## AC-N: <name> sections, each with Priority, Type, and a domain-language body.

  8. Review panel — dispatch the standing adviser + advocate pair against acs.md per ${CLAUDE_PLUGIN_ROOT}/references/review-panel.md. This is the cheapest place in the pipeline to catch a wrong AC: atdd formalizes these into executable specs next, and everything downstream is derived from them. Autonomy-keyed (offer at low, auto at medium/high); skip silently on a trivial AC set. In reverse-engineer mode add the reverse-engineering clause to both briefs — an AC read back off working code is the exact case where unfalsifiable and merely-descriptive ACs slip through. Fold the findings into acs.md, then record every finding — accepted or rejected — as panel_findings[] in the handoff.

  9. Handoff — emit a summary.

Show full SKILL.md (276 more words)Show less

Re-invoking on a feature with existing acs.md is an edit pass (preserve AC IDs). Big restructures → feature-edit.

In reverse-engineer mode, note in the handoff that acs.md and the original spec should later be reconciled — a good consistency-check target.

Handoff

Emit per ${CLAUDE_PLUGIN_ROOT}/references/handoff-summary.md. checkpoint: 2; human_action_needed: yes (review); recommended_next: "/engineer.atdd to formalize as Given/When/Then specs" (greenfield), or "/engineer.consistency-check to reconcile acs.md against the existing spec" (reverse-engineer).

The handoff MUST include the exit_criteria block asserting each of Checkpoint 2's exit criteria (Foundation Design Section 8) with verified_by, met, and evidence. For verified_by: tool criteria, the evidence MUST be the tool's actual output. The checkpoint is marked done only when every criterion is met.

ACs ship with human_action_needed: yes (the human owns the AC contract) — so this checkpoint is one of the explicit stop points per ${CLAUDE_PLUGIN_ROOT}/references/handoff-dispatch.md. Present the ACs for review; do not auto-dispatch CP3 atdd until the human has approved them.

Unless the feature's gate_profile.front says otherwise, and only at autonomy_level medium/high (see ${CLAUDE_PLUGIN_ROOT}/references/gate-profile.md): under front: bundled or auto, the AC contract is not approved here — it is approved as part of the one front bundle at CP4 (bundled), or trusted to the back gate (auto). In those cases set human_action_needed: no, note front_gate: deferred in the handoff, and auto-dispatch CP3. Only when gate_profile is absent — or when autonomy_level is low (which suppresses front-dialing; the human is reviewing everything anyway) — does the standalone AC stop above apply. That is the backward-compatible / safety default.

References

  • ${CLAUDE_PLUGIN_ROOT}/references/handoff-dispatch.md — when to dispatch vs stop
  • ${CLAUDE_PLUGIN_ROOT}/references/review-panel.md — the Step 8 adviser + advocate gate
  • ${CLAUDE_PLUGIN_ROOT}/references/ac-coverage/README.md — index of domain-aware coverage checklists
  • Foundation Design — feature.md schema
  • The DAE methodology page — why ACs and specs are separate

© swingerman, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in engineer/skills/discover-acs of swingerman/engineer.

Open the folder on GitHubat commit 32947eb

Compare with similar skills

Discover Acs next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

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Ralph Tui Create Beads Rustsubsy/ralph-tui2.5k1 repos~2.8kAutomated safety check: PassMIT
To Specbestofjs/bestofjs3.1k21 repos~757Automated safety check: PassMIT

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Questions about Discover Acs

What does Discover Acs do?

A skill your agent uses when a Ready feature needs its acceptance criteria discovered before specs are written. Discover Acs is an agent skill from swingerman/engineer. Use when a Ready feature needs its acceptance criteria discovered before specs are written.

When should I use Discover Acs?

Discover Acs fits situations like: A Ready feature needs its acceptance criteria discovered before specs are written; — /engineer.discover-acs; /engineer.acceptance-criteria; what must this feature do.

How do I install Discover Acs in Claude Code?

Run `npx skills add swingerman/engineer --skill discover-acs -a claude-code`. Or copy the skill folder (engineer/skills/discover-acs in swingerman/engineer) into .claude/skills/discover-acs in your project. Claude Code loads it when a task matches its description.

How do I install Discover Acs in Codex?

Run `npx skills add swingerman/engineer --skill discover-acs -a codex`. Or copy the skill folder (engineer/skills/discover-acs in swingerman/engineer) into .agents/skills/discover-acs in your project. Codex loads it when a task matches its description.

Can I use Discover Acs in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add swingerman/engineer --skill discover-acs -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/discover-acs, .gemini/skills/discover-acs, .github/skills/discover-acs and .opencode/skills/discover-acs in your project.

What does Discover Acs need to run?

SKILL.md names no scripts, command-line tools or credentials: Discover Acs is instructions for the agent only.

Does Discover Acs access the network?

SKILL.md names 1 domain. As links in the text: notion.so. This is read from the text; nothing was executed.

Is Discover Acs safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Discover Acs use?

Discover Acs is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Discover Acs use?

About 2.2k tokens (SKILL.md is roughly 8.9k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Discover Acs?

Skills that share tags, products or a category with Discover Acs: User Story Writer (deanpeters/Product-Manager-Skills, 7.2k stars), Ralph Tui Create Beads (subsy/ralph-tui, 2.5k stars), Agile Product Owner (alirezarezvani/claude-skills, 28k stars) and Ralph Tui Create Beads Rust (subsy/ralph-tui, 2.5k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Discover Acs?

swingerman (a GitHub user) maintains it in swingerman/engineer, which has 154 GitHub stars. The repository holds 27 skills in this directory. The repository was last updated on September 23, 2026.

Source: swingerman/engineer on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.