Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add mattgierhart/PRD-driven-context-engineering --skill prd-v07-implementation-loopgit clone --depth 1 https://github.com/mattgierhart/PRD-driven-context-engineeringWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/mattgierhart/prd-driven-context-engineering/prd-v07-implementation-loop)<a href="https://agentmods.dev/skills/mattgierhart/prd-driven-context-engineering/prd-v07-implementation-loop"><img src="https://agentmods.dev/badge/skills/mattgierhart/prd-driven-context-engineering/prd-v07-implementation-loop/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/mattgierhart/prd-driven-context-engineering/prd-v07-implementation-loop"><img src="https://agentmods.dev/badge/skills/mattgierhart/prd-driven-context-engineering/prd-v07-implementation-loop.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00113 | $0.04774 |
| Opus 5.5 | $0.00045 | $0.01910 |
| Sonnet 5.5 | $0.00023 | $0.00955 |
| Haiku 4.5 | $0.00011 | $0.00477 |
Grade A, and why
prd-v07-implementation-loop scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 459 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Implementation Loop
Position in workflow: v0.7 Test Planning → v0.7 Implementation Loop → v0.8 Release
Consumes
This skill requires prior work from v0.7 Epic Scoping and v0.7 Test Planning:
- EPIC-* entries (from v0.7 Epic Scoping) — EPIC context, objectives, Context & IDs table, execution plan phases, Session State tracking
- TEST-* test specifications (from v0.7 Test Planning) — Acceptance criteria in Given-When-Then format; tests define "done" for each deliverable
- API-* endpoint contracts (referenced in EPIC Context & IDs) — Implementation targets with request/response shapes, error codes, constraints
- DBT-* schema specifications (referenced in EPIC Context & IDs) — Data model, field types, relationships, constraints to implement
- BR-* business rules (referenced in EPIC Context & IDs) — Product logic constraints to enforce in code
- Existing SoT files (if brownfield) — Durable specs that guide implementation without re-research
This skill assumes EPIC- and TEST- entries are complete, with all upstream IDs fully specified.
Produces
This skill updates/creates:
- Working code (implementation of API-, DBT-, BR-, tested against TEST-) — Runnable code with @implements tags tracing back to specifications; passes all TEST- for EPIC
- Updated SoT entries (if implementation reveals changes) — When building reveals new constraints or edge cases, update API-/DBT-/BR- entries immediately (not deferred)
- Session State updates (EPIC.md Section 1) — "Brain dump" tracking exact stopping point, Next Steps for resume, blockers, decisions, Context
- Development Graph (
status/devgraph.json) — the@implements/@verifiestags you write are harvested into bridge edges, producing the as-built layer that readiness scores (implementation_coverage,architecture_conformance) and the HeartBeat visualizer renders. Schema:docs/DEVELOPMENT_GRAPH.md.
All implementation outputs are code and live SoT, not confidence-based. They are:
- Traceable (every function tagged with @implements pointing to specification ID)
- Tested (all TEST- for EPIC pass before marking phase/EPIC complete)
- SoT-synchronized (implementation matches specs/ or specs/ updated to match implementation reality)
- Session-state-preserved (Session State section allows seamless resume from exact stopping point)
What ships with it
6 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 459 lines · 113 tokens per session scan A 1def7f2dcb64
prd-v07-implementation-loop is a skill published in the GitHub repository mattgierhart/PRD-driven-context-engineering (181 stars, last pushed 1mo ago), licensed MIT. It adds 113 tokens to every session and 4,774 once invoked, about $0.0005 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
tdd
Test-first at pre-agreed seams — one test, one implementation, tracer-bullet red/green; independent expected values; substitutions only at the seam's boundary class; launch Phase 4 reference.
setup
Set up or update TDD Guard for the current project. Detects the test framework, installs or updates the matching reporter, and configures or migrates its configuration to match the current specification.
tdd
Build this test-first, one behavior at a time: $ARGUMENTS.
implement
Execute an approved phase plan with TDD, dependency-aware task fan-out, required evidence, and a strict iteration handoff.
plan-pipeline-execute
Execute a validated plan: worktree isolation, TDD scaffolding, level-based parallel agents, quality gate with smoke test, PR creation and merge. Handles everything through to merged PR.
linked-intent-dev
Guide for linked-intent development (LID). Consult for ALL code changes. Walks changes through a mode-aware six-phase workflow (HLD → LLD → EARS → intent-narrowing edge audit → tests-first → code) with mandatory stops between each phase. Bugs walk the arrow like any other change — no short-circuit. Enforces cascade…