detective-contracts

detective-contracts is an agent for Claude Code from felvieira/claude-skills-fv. It costs 74 tokens per session (1,051 once invoked), scanned A, original, Apache-2.0.

A read-only assistant that investigates the contract of a module in an older codebase: its public interface, dependencies, rules, and users.

In plain words
What is it for?
Use it to analyze a file, directory, or package and produce documentation of its exported functions, direct imports, constraints, and consumers.
Why use it?
It turns hard-to-understand module behavior into documented evidence without modifying the source code.

Agent for Claude Code

Written for Claude Code: a Claude Code subagent (agents/*.md). Also seen: model in frontmatter; mentions subagents; positional $N argument.

Part of the dev-team-kit-fv plugin — 72 skills, 45 commands, 16 agents, 5 hooks shipped together

Good fit Use it to analyze a file, directory, or package and produce documentation of its exported functions, direct imports, constraints, and consumers.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/felvieira/claude-skills-fv/detective-contracts
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.

Clone the repo
git clone --depth 1 https://github.com/felvieira/claude-skills-fv

Made for: Claude Code.

Or install dev-team-kit-fv, the plugin that ships this one along with the rest of its 72 skills, 45 commands, 16 agents, 5 hooks.

Wrote 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.

agentmods badge for detective-contracts

README.md
[![agentmods](https://agentmods.dev/badge/agents/felvieira/claude-skills-fv/detective-contracts/github.svg)](https://agentmods.dev/agents/felvieira/claude-skills-fv/detective-contracts)
Your own site
<a href="https://agentmods.dev/agents/felvieira/claude-skills-fv/detective-contracts"><img src="https://agentmods.dev/badge/agents/felvieira/claude-skills-fv/detective-contracts/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for detective-contracts

Your own site · 80×15
<a href="https://agentmods.dev/agents/felvieira/claude-skills-fv/detective-contracts"><img src="https://agentmods.dev/badge/agents/felvieira/claude-skills-fv/detective-contracts.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 74 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,051 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00074 $0.01051
Opus 5 $0.00037 $0.00526
Sonnet 5 $0.00015 $0.00210
Haiku 4.5 $0.00007 $0.00105

Measured 13d ago against content hash 1c70f30ab204, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

detective-contracts 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 13d 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/detective-contracts.md · 108 lines

How it starts

The opening of the file, as written. The whole thing — 108 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Protocol Shell

# protocol: detective-contracts v1.0
intent: "Extract module contracts (API surface, deps, invariants, consumers) from legacy code — read-only"

input:
  module_path: path           # directory or file to analyze
  scope: enum(file|dir|pkg)   # analysis granularity (default: dir)
  depth: enum(shallow|deep)   # shallow=API only, deep=internals (default: shallow)

process:
  - /scan.public_api{target=input.module_path}
  - /extract.dependencies{filter='direct_only'}
  - /identify.invariants{confidence_threshold=0.7}
  - /map.consumers{scope=input.scope}
  - /output.contract_doc{format='_detective_sdd/01-modules/<name>.md'}

output:
  contract_path: path         # written file in _detective_sdd/01-modules/
  public_api: list<string>    # exported symbols
  dependencies: list<string>  # direct imports
  invariants: list<string>    # identified constraints
  confidence: high|medium|low

meta:
  version: "1.0.0"
  skill_ref: "skills/33-detective-spec/SKILL.md"
  allowed_tools: [Read, Grep, Glob, Bash]

Detective Contracts — Subagent

Você é o detetive de contratos de módulo. Investiga código legado em modo read-only absoluto (governado por policies/detective-write-guardrails.md) e produz contratos operacionais em _detective_sdd/01-modules/<name>.md.

Este subagent e auto-contido — o protocolo essencial esta inline abaixo. Se o repo tiver personas/detective-contracts.md (instalado via /devkit-install-fv ou setup/install.sh), use-o como referencia estendida com exemplos. Em instalacao via plugin global (Claude Code), siga apenas o que esta neste arquivo.

Protocolo Essencial — 7 Perguntas por Módulo

  1. Responsabilidade (1-2 linhas)
  2. API Pública — funções/classes/endpoints exportados, com [evidence: file:line]
  3. Dependências — internas, externas, side effects
  4. Invariantes — o que o código assume verdadeiro sem checar
  5. Consumidores — call sites principais (Grep)
  6. Estado Interno — vars de módulo, singletons, caches
  7. Suspeitas — dead code candidato, TODOs, dynamic dispatch

Read the full file on GitHub · 108 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. 13d ago First seen · 108 lines · 74 tokens per session scan A 1c70f30ab204

Subscribe to this mod's changes

detective-contracts is an agent published in the GitHub repository felvieira/claude-skills-fv (23 stars, last pushed today), licensed Apache-2.0. It adds 74 tokens to every session and 1,051 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.