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 agentmods add skills/fattain-naime/engineering-docs/implementation-plannpx skills add fattain-naime/engineering-docs --skill implementation-plangit clone --depth 1 https://github.com/fattain-naime/engineering-docsWhat 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 | $0.00070 | $0.03538 |
| Opus 5 | $0.00035 | $0.01769 |
| Sonnet 5 | $0.00014 | $0.00708 |
| Haiku 4.5 | $0.00007 | $0.00354 |
Grade A, and why
implementation-plan 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 yesterday.
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 — 240 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Purpose
Produce an implementation plan that sequences the technical build of a project into ordered phases, driven by dependency rather than preference, with an explicit Definition of Ready and Definition of Done for each phase.
Build order is a technical decision with real consequences, not a scheduling afterthought. Building a feature before its data foundation exists means rework; building the UI before the API contract is frozen means integration churn. This document exists so those decisions are made once, deliberately, instead of discovered mid-build.
Input
Works best with: The project or system name, plus its architecture and/or requirements if they exist. Also valuable: The system-architecture-document, technical-specification, and project-plan for this project if already written - this skill sequences their contents rather than re-deriving them.
Example invocation: Create an implementation plan for our new marketplace platform. We have the architecture doc (Next.js frontend, Node/Postgres backend, Stripe Connect for payouts) and the technical spec. Sequence the build so an AI coding agent could execute it phase by phase without needing to ask what to build next.
Key Concepts
Foundation Before Features
Certain components block almost everything else and must be built first regardless of what feels most important to stakeholders: data model/schema, authentication and authorization, core API scaffolding, CI/CD and environment setup. Sequencing feature work before these exist guarantees rework.
Dependency-Driven Phases, Not Calendar Phases
A phase boundary should represent a real technical dependency ("Phase 2 cannot start until the data model in Phase 1 is migrated and tested"), not an arbitrary time slice. If two workstreams have no dependency on each other, they belong in the same phase, done in parallel.
Definition of Ready / Definition of Done (per phase)
- Definition of Ready: What must be true before work on this phase can begin (e.g., "API contract for Phase 2 is frozen and reviewed").
- Definition of Done: What must be true before moving to the next phase (e.g., "all Phase 1 endpoints pass integration tests against a seeded database"). Vague phase boundaries ("mostly done") are the most common cause of premature integration and cascading bugs.
What ships with it
1 file 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.
- yesterday First seen · 240 lines · 70 tokens per session scan A 64ecf5978280
implementation-plan is a skill published in the GitHub repository fattain-naime/engineering-docs (4 stars, last pushed 17d ago), licensed MIT. It adds 70 tokens to every session and 3,538 once invoked, about $0.0003 per session on Opus 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 2026-08-31.
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