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 kid-sid/codex-spellbook --skill requirements-planninggit clone --depth 1 https://github.com/kid-sid/codex-spellbookWrote 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/kid-sid/codex-spellbook/requirements-planning)<a href="https://agentmods.dev/skills/kid-sid/codex-spellbook/requirements-planning"><img src="https://agentmods.dev/badge/skills/kid-sid/codex-spellbook/requirements-planning.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00041 | $0.02928 |
| Opus 5 | $0.00020 | $0.01464 |
| Sonnet 5 | $0.00008 | $0.00586 |
| Haiku 4.5 | $0.00004 | $0.00293 |
Grade A, and why
requirements-planning 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 7d 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 — 315 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Requirements Planning
A complete reference for writing requirements that are clear, testable, and ready for development — from individual user stories to full PRDs.
When to Activate
- Writing a PRD, one-pager, or product requirements document
- Creating user stories or acceptance criteria for a feature
- Story pointing or sprint planning
- Breaking down an epic into implementable tasks
- Defining Done criteria for a story or sprint
- Reviewing whether requirements are testable and complete
User Stories
INVEST Criteria
Every well-formed user story satisfies all six INVEST properties.
| Criteria | Meaning | Test question |
|---|---|---|
| Independent | Can be developed without depending on another story | "Can this be built and deployed alone?" |
| Negotiable | Details can be discussed, not a rigid contract | "Is there flexibility in the how?" |
| Valuable | Delivers value to a user or stakeholder | "Who benefits and how?" |
| Estimable | Team can roughly size it | "Do we know enough to estimate?" |
| Small | Can be completed in one sprint | "Can one developer finish this in ≤5 days?" |
| Testable | Acceptance criteria can be verified | "How will we know it's done?" |
Story Format
As a <role>,
I want to <action>,
so that <benefit>.
BAD — This is a task disguised as a story:
As a developer,
I want to implement the login endpoint,
so that the API exists.
GOOD — Clear role, action, and benefit:
As a returning user,
I want to log in with my email and password,
so that I can access my account and personal data.
Common Anti-Patterns
- Story is a task — "Implement the login endpoint" describes technical work, not user value. Reframe around what the user can do.
- No acceptance criteria — Without AC, there is no shared definition of done. Write AC before any code is written.
- Story spans multiple sprints — If a story cannot be completed in a single sprint, split it using vertical slicing (see below).
- Story says how instead of what — Requirements describe the desired outcome, not the implementation. Leave the how to the team.
- Passive voice hides the actor — "Notifications should be sent" — by whom? to whom? Make the subject explicit.
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.
- 7d ago First seen · 315 lines · 41 tokens per session scan A 5f38144e9f9e
requirements-planning is a skill published in the GitHub repository kid-sid/codex-spellbook (21 stars, last pushed 3mo ago), licensed MIT. It adds 41 tokens to every session and 2,928 once invoked, about $0.0002 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 2026-08-30.
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