code-to-spec

A project-documentation tool that reads an existing codebase and produces a structured specification, or SPEC, describing what it does and how it is built.

In plain words
What is it for?
Use it to inspect project files, configuration, tests, and structure; document the system; prepare a rewrite or refactor; or onboard contributors.
Why use it?
It gives developers a shared explanation of a project when little documentation exists or when the code may differ from people’s assumptions.

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/smallnest/pigo/code-to-spec
Any agent
npx skills add smallnest/pigo --skill code-to-spec
Clone the repo
git clone --depth 1 https://github.com/smallnest/pigo

Made for: Claude Code, Codex.

Per session 81 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,398 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 $0.00081 $0.02398
Opus 5 $0.00041 $0.01199
Sonnet 5 $0.00016 $0.00480
Haiku 4.5 $0.00008 $0.00240

Measured 2d ago against content hash 523fd108b00d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

code-to-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 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.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

internal/builtinskills/skills/code-to-spec/SKILL.md · 342 lines

How it starts

The opening of the file, as written. The whole thing — 342 lines — stays where its author put it; the contents beside it link to each section on GitHub.

to-spec — Reverse-Engineer Project Specification

Analyze an existing codebase and produce a structured SPEC document that captures what the project does, how it's built, and what contracts it exposes. The output is a living specification that could be used to rebuild the project from scratch or onboard new contributors.


When to Use

  • You want a comprehensive understanding of an existing project
  • Onboarding new team members who need a high-level overview
  • Documenting a project that was built without a spec
  • Comparing actual implementation against intended design
  • Preparing for a rewrite or major refactor
  • Auditing what a project actually does vs. what people think it does

The Job

  1. Scope confirmation — ask user what to analyze (entire repo, specific directory, or specific aspect)
  2. Deep scan — systematically read project structure, entry points, config, tests, and core logic
  3. Synthesize — produce a structured SPEC document
  4. Review — present to user for feedback and iteration
  5. Save — write final SPEC to agreed location

Step 1: Scope Confirmation

Before scanning, ask the user:

What should I analyze?

A. Entire repository (recommended for small-medium projects)
B. Specific directory or module: [path]
C. Specific aspect only (e.g., API surface, data model, auth flow)

Depth level:
1. Overview — high-level architecture + tech stack + key features (fast, ~5 min)
2. Standard — includes API contracts, data models, config, dependencies (default)
3. Deep — adds internal module interactions, error handling patterns, test coverage analysis

If the project is large (>500 files), recommend starting with Overview or a specific module.


Step 2: Deep Scan

Systematically analyze the following (adapt to what exists):

2.1 Project Identity

  • package.json, go.mod, Cargo.toml, pyproject.toml, pom.xml, etc.
  • README, LICENSE
  • Git history (first commit date, recent activity, contributor count)

Read the full file on GitHub · 342 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. 2d ago First seen · 342 lines · 81 tokens per session scan A 523fd108b00d

Subscribe to this mod's changes

code-to-spec is a skill published in the GitHub repository smallnest/pigo (403 stars, last pushed 2d ago), licensed MIT. It adds 81 tokens to every session and 2,398 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 2026-08-30.