api-sec

api-sec is a skill for Claude Code, Codex from JustineDevs/premortem. It costs 36 tokens per session (599 once invoked), scanned A, a copy of api-sec, Apache-2.0.

A starting guide for API security testing, covering REST APIs, mobile backends, and GraphQL, a query-based API system. It routes findings to separate areas such as documentation, authorization, tokens, and hidden parameters.

In plain words
What is it for?
Use it to triage OpenAPI or Swagger documentation, object IDs, JWT bearer tokens, GraphQL endpoints, batched requests, and undocumented or writable fields.
Why use it?
It helps choose the right testing path before investigating a specific API weakness.

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/justinedevs/premortem/api-sec
Any agent
npx skills add JustineDevs/premortem --skill api-sec
Clone the repo
git clone --depth 1 https://github.com/JustineDevs/premortem

Made for: Claude Code, Codex.

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 api-sec

README.md
[![agentmods](https://agentmods.dev/badge/skills/justinedevs/premortem/api-sec.svg)](https://agentmods.dev/skills/justinedevs/premortem/api-sec)
Your own site
<a href="https://agentmods.dev/skills/justinedevs/premortem/api-sec"><img src="https://agentmods.dev/badge/skills/justinedevs/premortem/api-sec.svg" alt="Measured on agentmods" height="20"></a>
Per session 36 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 599 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod 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 $0.00036 $0.00599
Opus 5 $0.00018 $0.00300
Sonnet 5 $0.00007 $0.00120
Haiku 4.5 $0.00004 $0.00060

Measured 3d ago against content hash d3da8c0ed9b1, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

api-sec 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 3d 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

This is a copy

100% identical to api-sec — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.agents/skills/api-sec/SKILL.md · 49 lines

How it starts

The opening of the file, as written. The whole thing — 49 lines — stays where its author put it; the contents beside it link to each section on GitHub.

API Security Router

This is the routing entry point for API security testing.

Use this skill first to decide whether the API issue is mostly recon/docs, object authorization, token trust, or GraphQL/hidden parameters, then route to a deeper topic skill.

When to Use

  • The target exposes REST APIs, mobile backends, or GraphQL endpoints
  • You need to define API testing order before going into specific topics
  • You want to handle object authorization, JWT, GraphQL, and hidden fields as separate tracks

Skill Map

Quick Triage

Observation Route
Swagger or OpenAPI is present api-recon-and-docs
IDs appear in URL, JSON, headers, or GraphQL args api-authorization-and-bola
JWT token visible in traffic api-auth-and-jwt-abuse
/graphql or batched JSON arrays are present graphql-and-hidden-parameters
Registration, login, or profile updates accept extra fields api-authorization-and-bola then api-auth-and-jwt-abuse
  1. Start with exposed endpoints and documentation assets
  2. Then evaluate object-level and function-level authorization
  3. Then evaluate token, header, signature, and rate-limit boundaries
  4. If GraphQL or complex JSON is present, continue with hidden fields and schema abuse

Read the full file on GitHub · 49 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. 3d ago First seen · 49 lines · 36 tokens per session scan A d3da8c0ed9b1

Subscribe to this mod's changes

api-sec is a skill published in the GitHub repository JustineDevs/premortem (2 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 36 tokens to every session and 599 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to api-sec, differing in 0 lines, and is treated as a copy.

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