implement-feature

A guided workflow for building a software feature from an existing design document. It requires the design and an approved work plan before coding begins.

In plain words
What is it for?
Use it when a feature has already been designed and needs to be analyzed, coded, tested, and summarized.
Why use it?
It reduces the risk of implementing the wrong requirements or skipping tests, reviews, and integration checks.

Cursor rule for Cursor

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 rules/janekbaraniewski/openusage/implement-feature
Clone the repo
git clone --depth 1 https://github.com/janekbaraniewski/openusage

Made for: Cursor.

Per session 29 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 203 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 $0.00029 $0.00203
Opus 5 $0.00015 $0.00102
Sonnet 5 $0.00006 $0.00041
Haiku 4.5 $0.00003 $0.00020

Measured 2d ago against content hash b17e1b1f0319, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

implement-feature 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 2d 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.

.cursor/skills/implement-feature.mdc · 21 lines

What it actually says

@docs/skills/implement-feature/SKILL.md contains the full skill specification. Read and follow it completely.

The user's request is to implement the feature "$ARGUMENTS" from its design doc.

Follow all phases in order:

  1. Phase 0: Load the design doc, extract tasks
  2. Phase 1: Analyze the codebase for affected files
  3. Phase 1.5: Pre-implementation quiz for ambiguities
  4. Phase 2: Present execution plan, wait for approval
  5. Phase 3: Execute tasks with tests, parallel where possible
  6. Phase 4: Integration check (build, test, lint)
  7. Phase 5: Summary of all changes

Do NOT skip loading the design doc. Do NOT code without an approved plan.

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. 2d ago First seen · 21 lines · 29 tokens per session scan A b17e1b1f0319

Subscribe to this mod's changes

implement-feature is a cursor rule published in the GitHub repository janekbaraniewski/openusage (180 stars, last pushed 8d ago), licensed MIT. It adds 29 tokens to every session and 203 once invoked, about $0.0001 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.