implement

A workflow for turning a software specification into working code by writing tests for each requirement first, then implementing and checking the result.

In plain words
What is it for?
Use it to extract acceptance criteria, create tests before code, implement until the tests pass, check edge cases, and report what was completed.
Why use it?
It breaks a large coding task into testable requirements and catches missing behavior or regressions during development.

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/kastalien-research/thoughtbox/implement
Any agent
npx skills add Kastalien-Research/thoughtbox --skill implement
Clone the repo
git clone --depth 1 https://github.com/Kastalien-Research/thoughtbox

Made for: Claude Code, Codex.

Per session 34 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 425 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 $0.00034 $0.00425
Opus 5 $0.00017 $0.00212
Sonnet 5 $0.00007 $0.00085
Haiku 4.5 $0.00003 $0.00042

Measured 2d ago against content hash 7f8489940dfa, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

implement 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.

.agents/skills/implement/SKILL.md · 57 lines

What it actually says

Implement the following specification: $ARGUMENTS

Workflow

Phase 1: Requirement Extraction (10% of effort)

  1. Read the spec file (if a path was given) or parse the description
  2. Extract atomic, testable requirements
  3. Identify dependencies (internal and external)
  4. Create a checklist of acceptance criteria

Phase 2: Test-First Development (25% of effort)

For each requirement:

  1. Write a failing test that captures the requirement
  2. Run the test to confirm it fails (red)
  3. Move to the next requirement

Phase 3: Implementation (50% of effort)

For each failing test (in dependency order):

  1. Implement the minimum code to make the test pass
  2. Run the test to confirm it passes (green)
  3. Refactor if needed (keeping tests green)
  4. Check for regressions after each change

Spiral detection: If you find yourself editing the same files 3+ times without making progress, stop and reassess your approach.

Phase 4: Verification (15% of effort)

  1. Run the full test suite
  2. Walk through each acceptance criterion — does the implementation satisfy it?
  3. Check for edge cases not covered by tests
  4. Report results

Output

At completion, present:

## Implementation Summary

Requirements: [N total, N implemented, N deferred]
Tests: [N passing, N failing, N skipped]
Files changed: [list]

Acceptance Criteria:
  - [criterion 1]: PASS | FAIL
  - [criterion 2]: PASS | FAIL

Deferred items (if any):
  - [item]: [reason deferred]
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 · 57 lines · 34 tokens per session scan A 7f8489940dfa

Subscribe to this mod's changes

implement is a skill published in the GitHub repository Kastalien-Research/thoughtbox (64 stars, last pushed 1mo ago), licensed MIT. It adds 34 tokens to every session and 425 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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