openapi

openapi is a skill for Claude Code, Codex from alphabravo-oss/guild. It costs 40 tokens per session (461 once invoked), scanned A, a copy of openapi-spec-generation, MIT.

A guide for creating and maintaining OpenAPI 3.1 specifications. OpenAPI is a standard format for describing how a web API works, including its endpoints, data, and security rules.

In plain words
What is it for?
Use it to design or generate API specifications, validate implementations, document endpoints, and generate client software development kits.
Why use it?
It helps keep API documentation and implementation aligned and makes the API contract easier to validate and share.

Skill for Claude CodeCodex

Part of the webster plugin — 11 skills, 6 agents shipped together

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/alphabravo-oss/guild/openapi
Any agent
npx skills add alphabravo-oss/guild --skill openapi
Clone the repo
git clone --depth 1 https://github.com/alphabravo-oss/guild

Made for: Claude Code, Codex.

Or install webster, the plugin that ships this one along with the rest of its 11 skills, 6 agents.

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 openapi

README.md
[![agentmods](https://agentmods.dev/badge/skills/alphabravo-oss/guild/openapi.svg)](https://agentmods.dev/skills/alphabravo-oss/guild/openapi)
Your own site
<a href="https://agentmods.dev/skills/alphabravo-oss/guild/openapi"><img src="https://agentmods.dev/badge/skills/alphabravo-oss/guild/openapi.svg" alt="Measured on agentmods" height="20"></a>
Per session 40 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 461 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 92% 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 $0.00040 $0.00461
Opus 5 $0.00020 $0.00230
Sonnet 5 $0.00008 $0.00092
Haiku 4.5 $0.00004 $0.00046

Measured yesterday against content hash 3a887697df9c, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

openapi 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 yesterday.

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

92% identical to openapi-spec-generation — 2 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.

plugins/webster/skills/openapi/SKILL.md · 67 lines

What it actually says

OpenAPI Spec Generation

Comprehensive patterns for creating, maintaining, and validating OpenAPI 3.1 specifications for RESTful APIs.

When to Use This Skill

  • Creating API documentation from scratch
  • Generating OpenAPI specs from existing code
  • Designing API contracts (design-first approach)
  • Validating API implementations against specs
  • Generating client SDKs from specs
  • Setting up API documentation portals

Core Concepts

1. OpenAPI 3.1 Structure

openapi: 3.1.0
info:
  title: API Title
  version: 1.0.0
servers:
  - url: https://api.example.com/v1
paths:
  /resources:
    get: ...
components:
  schemas: ...
  securitySchemes: ...

2. Design Approaches

Approach Description Best For
Design-First Write spec before code New APIs, contracts
Code-First Generate spec from code Existing APIs
Hybrid Annotate code, generate spec Evolving APIs

Templates and detailed worked examples

Full template library and detailed worked examples live in references/details.md. Read that file when you need the concrete templates.

Best Practices

Do's

  • Use $ref - Reuse schemas, parameters, responses
  • Add examples - Real-world values help consumers
  • Document errors - All possible error codes
  • Version your API - In URL or header
  • Use semantic versioning - For spec changes

Don'ts

  • Don't use generic descriptions - Be specific
  • Don't skip security - Define all schemes
  • Don't forget nullable - Be explicit about null
  • Don't mix styles - Consistent naming throughout
  • Don't hardcode URLs - Use server variables
Files

What ships with it

2 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.

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. yesterday First seen · 67 lines · 40 tokens per session scan A 3a887697df9c

Subscribe to this mod's changes

openapi is a skill published in the GitHub repository alphabravo-oss/guild (2 stars, last pushed 3d ago), licensed MIT. It adds 40 tokens to every session and 461 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 92% identical to openapi-spec-generation, differing in 2 lines, and is treated as a copy.

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