Spec Kit SDD

This skill drives GitHub's Spec Kit through its full spec-driven development loop, so you write an explicit specification, plan, and task list before any implementation code exists. It's aimed at developers who want an AI agent to build against a reviewed, version-controlled intent — not a vibe-coded prompt — and who care about traceability from requirement to commit.

When to use it

• Starting a new feature where the requirements still have open questions you want surfaced and resolved up front.
• Working on a team that reviews specs and plans in PRs before code lands.
• Re-architecting an existing module and you want a checked-in plan.md, data model, and contracts to align on first.
• You keep getting half-right AI output because the agent guessed at acceptance criteria — EARS-style specs force those into the open.

How it works

The skill scaffolds a project with specify init (CLI installable via uv tool install specify-cli from the spec-kit repo), then runs the slash-command workflow inside your agent:

• /constitution — write memory/constitution.md with non-negotiable engineering principles (testing, library-first, observability) that every later step must respect.
• /specify — produce spec.md: user stories and acceptance criteria, written in EARS phrasing ("WHEN <trigger>, the system SHALL <response>").
• /clarify — interrogate the spec for ambiguities and underspecified behavior, recording answers back into spec.md.
• /plan — generate plan.md plus supporting artifacts: research.md, data-model.md, and a contracts/ directory.
• /tasks — derive an ordered, dependency-aware tasks.md.
• /analyze — cross-check spec, plan, and tasks for inconsistencies before you commit to building.
• /implement — execute the task list against the plan.

Artifacts live under a per-feature directory (e.g. specs/001-feature-name/) so each feature carries its own spec, plan, and tasks in git.

Usage example

curl -fsSL --create-dirs -o ~/.claude/skills/spec-driven-development-spec-kit/SKILL.md https://claudeskil.com/skills/spec-driven-development-spec-kit/SKILL.md

# scaffold (Spec Kit CLI)
uv tool install specify-cli --from git+https://github.com/github/spec-kit.git
specify init my-app
cd my-app

# then, inside your agent:
/constitution Principles: test-first, no feature without a contract
/specify Build a URL shortener with custom slugs and click analytics
/clarify
/plan Use Postgres, FastAPI, expose REST contracts under /api
/tasks
/analyze
/implement

Tips & gotchas

• Run /clarify before /plan — planning over an ambiguous spec bakes the wrong assumptions into data-model.md and contracts.
• The constitution is enforced downstream; vague principles produce vague gates. Make them checkable ("every endpoint has a contract test").
• /analyze is read-only triage — it reports drift but won't fix it. Re-run /specify or /plan to reconcile.
• Spec Kit is agent-agnostic; the same spec.md/plan.md work across Claude, Copilot, Cursor, and others.

FAQ

Do I have to use every command? No. The common minimum is /specify → /plan → /tasks → /implement. Add /constitution, /clarify, and /analyze as your need for rigor grows.

Does it overwrite my existing repo? specify init scaffolds the .specify/templates structure; use specify init --here to add it into the current directory rather than creating a new one.

Where do the specs live? Committed under specs/<feature>/, so they review and diff like code.