Getting it into your agent
There is no command for this one: it runs only inside a plugin, and the catalogue could not identify which plugin ships it. The source is linked below.
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.
[](https://agentmods.dev/skills/j4flmao/agent-skills/openapi-documentation)<a href="https://agentmods.dev/skills/j4flmao/agent-skills/openapi-documentation"><img src="https://agentmods.dev/badge/skills/j4flmao/agent-skills/openapi-documentation.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00103 | $0.04385 |
| Opus 5 | $0.00051 | $0.02193 |
| Sonnet 5 | $0.00021 | $0.00877 |
| Haiku 4.5 | $0.00010 | $0.00439 |
Grade A, and why
backend-openapi-documentation 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.
How it starts
The opening of the file, as written. The whole thing — 592 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Backend OpenAPI Documentation
Purpose
Drive all API development with an OpenAPI 3.x spec-first workflow: spec defines the contract, code is generated from it, and the spec is versioned alongside the code. The OpenAPI spec is the single source of truth for the API contract.
Agent Protocol
Trigger
Exact user phrases: "OpenAPI", "Swagger", "API documentation", "spec-first", "API spec", "openapi.yaml", "swagger.json", "codegen", "openapi-generator", "API contract first".
Input Context
- Existing API endpoints or resource definitions.
- Chosen OpenAPI version (3.0.x or 3.1.x).
- Code generation target language.
Output Artifact
OpenAPI YAML/JSON spec snippet or full spec file. No file unless requested.
Response Format
Path: {path}
Method: {method}
OperationId: {operationId}
Tags: [{tag}]
Completion Criteria
- Every endpoint has: path, method, operationId, summary, tags.
- Every request/response has a schema.
- All schemas use $ref and are not inline.
- Error responses documented.
- Security schemes defined.
- Spec passes validation (spectral or swagger-cli).
Max Response Length
6 lines per endpoint. Unlimited for full spec.
Architecture Decision Tree
Spec-First vs Code-First
Who owns the API contract?
├── Spec-first (OpenAPI as source of truth)
│ ├── PRO: Contract before implementation, generates client/server code
│ ├── CON: Slower initial development, requires spec discipline
│ └── Use when: Public API, multiple consumers, external integrations
└── Code-first (annotations/comments generate spec)
├── PRO: Faster development, single source (code)
├── CON: Spec is afterthought, easy to forget docs
└── Use when: Internal API, single consumer, rapid prototyping
OpenAPI Version Decision
Do you need JSON Schema full compatibility?
├── Yes → OpenAPI 3.1.x (fully compatible with JSON Schema 2020-12)
│ ├── PRO: $ref anywhere, JSON Schema ecosystem
│ └── CON: Less tooling support, newer standard
└── No → OpenAPI 3.0.x (wider tool support)
├── PRO: Most tools support this (Swagger UI, codegen, Spectral)
└── CON: Limited JSON Schema compatibility
What ships with it
6 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 2d ago First seen · 592 lines · 103 tokens per session scan A 3f4286021a3a
backend-openapi-documentation is a skill published in the GitHub repository j4flmao/agent-skills (20 stars, last pushed today), licensed MIT. It adds 103 tokens to every session and 4,385 once invoked, about $0.0005 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 2026-09-03.
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