Implement Skill: A 7-Line Spec That Routes AI Coding Work

The most important skill in Matt Pocock’s engineering family is the one that barely exists. Implement’s SKILL.md holds seven lines of instruction, yet the skill sits at #92 on the skills.sh all-time leaderboard with 412.3K installs. I pulled the file from the mattpocock/skills repo (233K stars) and read it next to its siblings tdd, to-spec, and code-review. What the seven lines do is route work, not write it. That routing is the actual feature.

It’s Built to Never Fire on Its Own

Implement’s frontmatter opens with disable-model-invocation: true, and its OpenAI agent manifest repeats the decision: allow_implicit_invocation: false. Models cannot trigger this skill mid-session; a human must invoke it explicitly. Compare that to siblings in the same folder: tdd’s description fires on “red-green-refactor” or “integration tests”, prototype names its own scenarios, but implement and to-spec both demand a named handoff.

That split is deliberate. Implementation is where context collapses — an agent that auto-fires “implement” builds from whatever it half-remembered instead of the agreed spec. Blocking implicit invocation forces the handoff into the open: someone names the spec, the seams, and the branch before the coding starts.

What the Seven Lines Actually Say

The whole instruction body reads as a five-item routing list:

1. Implement the work described in the spec or tickets.
2. Use /tdd where possible, at pre-agreed seams.
3. Run typechecking regularly, single test files regularly, and the full test suite once at the end.
4. Review the work with /code-review when done.
5. Commit your work to the current branch.

Real talk: the cadence in item three is the discipline. “Pre-agreed seams” plugs straight into tdd’s hard rule — write down the seams under test and confirm them with the user before writing any test. No unconfirmed seam, no test. The rhythm of typecheck-often, single-file-often, full-suite-once keeps the loop tight while you build. And item four sits before item five on purpose: review gate, then commit. No branch hopping, no PR-shaped surprise at the end.

Where It Sits in the Assembly Line

Implement is step three of five in the family pipeline. Prototype cheaply answers the risky questions, to-spec publishes the conversation as a spec tagged ready-for-agent, implement builds to that spec, code-review audits the result, and diagnosing-bugs handles whatever still breaks. Previous write-ups here covered the bookends: code-review brings the 12-point Fowler smell baseline, and codebase-design supplies the glossary that keeps the vocabulary stable.

In that chain, implement’s job is purely connective. The seam list arrives pre-agreed from to-spec, the test loop comes from tdd, the review standard comes from code-review. The seven lines point the agent at the right hop and set the cadence between hops — which is why the skill looks thin next to a 200-line “coding best practices” checklist. A checklist describes good code. This skill describes a repeatable handoff, and repeatability is what makes the other four skills dependable.

Bottom Line

Implement is the least glamorous skill in the family and the one that makes the other four repeatable. Install the family with npx skills@latest add mattpocock/skills, pick implement alongside tdd and code-review, then try the explicit handoff on your next ticket: agree seams, build in vertical slices, review before commit. The seven lines won’t write your code — they guarantee the code that gets written is the code you actually specified.