mcaf-feature-spec

A feature-specification workflow for documenting how a non-trivial product feature should behave before or during implementation.

In plain words
What is it for?
Use it to create or update a feature document with business rules, diagrams, verification scenarios, implementation links, and a definition of done.
Why use it?
It replaces vague requirements with concrete rules, user flows, system behaviour, and checks that developers and testers can follow without guessing.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/managedcode/geminisharpsdk/mcaf-feature-spec
Any agent
npx skills add managedcode/GeminiSharpSDK --skill mcaf-feature-spec
Clone the repo
git clone --depth 1 https://github.com/managedcode/GeminiSharpSDK

Made for: Claude Code, Codex.

Per session 75 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 612 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00075 $0.00612
Opus 5 $0.00037 $0.00306
Sonnet 5 $0.00015 $0.00122
Haiku 4.5 $0.00007 $0.00061

Measured yesterday against content hash 7aeb0a2d0713, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

mcaf-feature-spec 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.

.codex/skills/mcaf-feature-spec/SKILL.md · 51 lines

How it starts

The opening of the file, as written. The whole thing — 51 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MCAF: Feature Spec

Outputs

  • docs/Features/<feature>.md (create or update)
  • Update links from/to ADRs and architecture map when needed

Spec Quality (anti-guesswork checklist)

Write a spec that can be implemented and verified without guessing:

  • No placeholders: avoid “TBD”, “later”, “etc.”; if something is unknown, list it as an explicit question.
  • Concrete modules: use real module/boundary names from docs/Architecture/Overview.md.
  • Rules are testable: numbered business rules with clear inputs → outputs (no vague adjectives).
  • Flows are executable: scenarios include preconditions, steps, expected results (happy + negative + edge).
  • Verification is real: commands copied from AGENTS.md, and scenarios mapped to test IDs.
  • Stakeholders covered: Product / Dev / DevOps / QA each get the information they need to ship safely.

Workflow

  1. Start from docs/Architecture/Overview.md to pick the affected module(s).
  2. Create/update the feature doc using docs/templates/Feature-Template.md.
    • follow AGENTS.md scoping rules (do not scan the whole repo; use the architecture map to stay focused)
    • keep the feature’s ## Implementation plan (step-by-step) updated while executing
  3. Define behaviour precisely:
    • purpose and scope (in/out)
    • business rules (numbered, testable)
    • primary flow + edge cases
  4. Describe system behaviour in terms of entry points, reads/writes, side effects, idempotency, and errors.
  5. Add a Mermaid diagram for the main flow (modules + interactions; keep it readable).
  6. Write verification that can be executed:
    • test environment assumptions
    • concrete test flows (positive/negative/edge)
    • mapping to where tests live (or will live)
    • traceability: rules/flows → test IDs (so tests reflect the spec)
  7. Keep Definition of Done strict:
    • behaviour covered by automated tests
    • static analysis clean
    • docs updated (feature + ADR + architecture overview if boundaries changed)

Read the full file on GitHub · 51 lines

Changes

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.

  1. yesterday First seen · 51 lines · 75 tokens per session scan A 7aeb0a2d0713

Subscribe to this mod's changes

mcaf-feature-spec is a skill published in the GitHub repository managedcode/GeminiSharpSDK (2 stars, last pushed 4mo ago), licensed MIT. It adds 75 tokens to every session and 612 once invoked, about $0.0004 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.