Spec Writing

spec-writing — research, grill the open questions, THEN write the spec

Input: a feature request. Output: a complete spec at .ai/specs/{YYYY-MM-DD}-{slug}.md written after every open question has been resolved with the user. The interview happens before the document exists, so the spec is written once, around real answers — not written around guesses and reworked after the fact.

The spec is the single design artifact. Do not write separate "design docs" in other locations.

Announce at start: "Using the spec-writing skill — designing {feature}; I'll bring you the open questions before writing the spec."

When to write a spec

Lifecycle and naming rules live in .ai/specs/AGENTS.md. Read it once before your first spec.

Step 1: Scope the request

If the request is ambiguous, ask the user at most 3–4 focused questions covering: what (the capability), why (the problem), where (ERP, MES, or both), who (the users). If the request is already clear, skip to Step 2.

Step 2: Read Carbon context

Run all of these before designing anything:

ls .ai/specs/ .ai/specs/implemented/ | grep -i {keyword}   # prior art — never duplicate a spec
cat .ai/lessons.md                                          # known pitfalls
cat .ai/docs/module-conventions.md                          # module layout rules
cat apps/erp/app/modules/{module}/AGENTS.md                 # for every module touched

Then read the .claude/rules/ files matching the domain (use the Task Router table in the root AGENTS.md to find them).

Step 3: Research competitors

Invoke /research {feature}. This is mandatory for ERP-domain features (accounting, costing, tax, inventory valuation, RMA, planning, etc.) — do not invent domain logic. Findings land in .ai/research/{slug}.md; cite that file from the spec.

Step 4: Make the design decisions — and separate the questions

For each significant decision (data model shape, status lifecycle, workflow, integration point):

1. State the question.
2. Cite what the research found ("SAP and NetSuite both…").
3. List 2–3 options with one-line trade-offs.
4. Decide it yourself if the research + codebase settle it — record the choice and rationale for the spec's Design Decisions table.
5. If you cannot settle it, it is an open question — genuine domain ambiguity, scope boundaries, data-model alternatives with real trade-offs, product-positioning calls, anything where the user's answer changes what you build. Do NOT pick a placeholder and move on; do NOT write "TBD".

Run every new or modified entity through this checklist; decided rows go in the Design Decisions table, unsettled ones join the question list:

At least one open question is required before proceeding. Zero questions means you haven't thought hard enough — re-read the research and the heuristics table.

Step 5: Grill — resolve the questions with the user BEFORE writing

🛑 HARD STOP: the spec file is not written while any question is unresolved.

Invoke /grill on the question list (protocol: .claude/skills/grill/SKILL.md — the spec doesn't exist yet, so this is its artifact-less mode; resolutions carry into the spec's Open Questions section when it is written in Step 6). Interview one question at a time (group max 2–3 only for single-module, no-schema designs). For each question:

• State the question and why it matters (what changes downstream).
• Give your recommended answer with a one-line rationale, plus the alternatives and their trade-offs.
• Cross-check the user's answer against the codebase before accepting it — if the answer contradicts something real (an existing table, a lesson in .ai/lessons.md, a prior spec), say so and re-ask.
• Record the resolution: - [x] {Question} — **Answer:** {decision and rationale}.

The user may batch ("accept all recommendations") — that is their call to make, not yours to assume. Never resolve a question yourself to unblock work; resolutions come only from a human answer, a research finding, or an explicit documented "out of scope for v1" decision.

Autonomous mode (automated loops — conductor, headless/outer-loop runs)

When this skill runs inside an automated loop with no human available, do not invoke /grill and do not block waiting for answers. Instead:

• Resolve each question in this order: (1) codebase precedent, (2) research / competitor consensus, (3) your recommended answer. Record it inline as - [x] {Question} — **Autonomous:** {answer + rationale} so assumed decisions are distinguishable from human ones at a glance.
• Surface the full list of autonomous resolutions in the spec changelog AND in the loop's "Assumed decisions" PR section — the human reviews them at the PR, not mid-loop.
• Ask-First territory is never resolved autonomously (root AGENTS.md: production-critical schema, auth/RBAC/multi-tenancy, public contracts, scope reductions, new production dependencies). A question in that territory → the loop goes BLOCKED with the question stated crisply.

Step 6: Write the spec

Only now. Copy .ai/specs/template.md to .ai/specs/{YYYY-MM-DD}-{slug}.md (today's date, kebab-case slug) and fill every section, with the Step-5 resolutions baked into the design. Rules:

• SQL sketches use id('prefix'), companyId, composite PK, audit columns — never gen_random_uuid().
• Acceptance criteria must be testable: "user creates a PO with 3 lines and sees correct totals in the list view", not "works correctly".
• No {placeholders} left in the file; mark inapplicable sections N/A with a reason.
• The Open Questions section records the resolved Q&A (all boxes checked, each with its inline answer) — it is the audit trail of Step 5, not a to-do list.

Step 7: New questions discovered while writing

Writing the spec sometimes surfaces questions Step 4 missed. When that happens:

• Add them to the Open Questions section as unchecked items with "why it matters".
• Take them back to the user (same protocol as Step 5) before calling the spec final — the hard stop applies to these too. Do not say "we can figure these out during implementation."

Step 8: Finalize

After every question is resolved: add a changelog entry, set status per .ai/specs/AGENTS.md. The spec is now ready for /plan (or /feature, which calls it).

Done when

• Every open question was answered by the user BEFORE the spec was written (Step 5), with the resolution recorded inline in the spec
• Spec exists at .ai/specs/{YYYY-MM-DD}-{slug}.md, every section real content, design reflecting the resolutions (no section contradicts an answer)
• Research file exists and is linked from the spec
• Every applicable heuristic (1–7) has a row in Design Decisions — no TBDs
• Any questions surfaced during writing (Step 7) were also resolved before the spec was called final

Anti-patterns

• Writing the spec first and interviewing the user afterward (the old flow — it produces rework: the document gets written around guesses, then edited around answers)
• Writing a design doc anywhere other than .ai/specs/
• Dumping all open questions in one message and accepting batch answers you assumed rather than the user chose
• Accepting an answer without checking it against the code
• Marking questions resolved without human input
• Skipping /research because "I know how ERPs work"
• "TBD" in the Design Decisions table (that's an open question — Step 5 it)
• Vague acceptance criteria ("feature works as expected")

Red flags — thinking any of these means the gate is being defeated; STOP:

• "I'll draft the spec now and confirm the questions after" (that IS the old flow)
• "I'll mark this question resolved so we can keep moving"
• "zero open questions — the design is clear" (you haven't looked hard enough)
• "we can settle this during implementation"
• "the user probably wants X, I'll assume it" (that assumption IS the question)