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Agent skill

Validating API Schemas

by jeremylongshore in jeremylongshore/tons-of-skills-marketplace

Validate API schemas against OpenAPI, JSON Schema, and GraphQL specifications.

MITAuto-check passedBackend & APIs

Install Validating API Schemas

skills CLI
$ npx skills add jeremylongshore/tons-of-skills-marketplace --skill validating-api-schemas -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install jeremylongshore/tons-of-skills-marketplace validating-api-schemas --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/jeremylongshore/tons-of-skills-marketplace.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/.curated/validating-api-schemas .claude/skills/validating-api-schemas && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
validating-api-schemas
GitHub stars
2.8k
Token cost
~1.3k tokens
SKILL.md length
553 words
Files
5 (incl. scripts, references)
Skills in repo
3,342
Repo updated
First seen
Licence
MIT

At a glance

Validate API schemas against OpenAPI, JSON Schema, and GraphQL specifications.

  • Works in 8 steps: Locate all API specification files using… → Run structural validation to verify the… → Apply Spectral linting rules to enforce… → …
  • Validating API schemas and contracts
  • SKILL.md covers Overview, Prerequisites, Instructions and Output, plus 3 more sections
  • Runs Shell scripts from its folder

What it does

Validating API Schemas is an agent skill from jeremylongshore/tons-of-skills-marketplace. Validate API schemas against OpenAPI, JSON Schema, and GraphQL specifications. Use when validating API schemas and contracts. Trigger with phrases like "validate API schema", "check OpenAPI spec", or "verify schema".

Its SKILL.md is about 1.3k tokens, which your agent loads only when the skill is triggered. The skill folder holds 6 other files, including scripts and reference files (for example `references/errors.md`, `references/examples.md` and `references/implementation.md`). Compatibility notes: Designed for Claude Code

It sits in Backend & APIs, covering OpenAPI specifications. It works with OpenAPI and GraphQL. The repository describes itself as: Model-agnostic agent-skills platform with a harness-free canonical layer, verified adapters, and the ccpi package manager. Explore at tonsofskills.com. The licence is MIT.

When your agent uses it

  • Validating API schemas and contracts
  • With phrases like validate API schema
  • Check OpenAPI spec

Example prompts

  • “validate API schema”
  • “check OpenAPI spec”
  • “verify schema”
  • “/validating-api-schemas”

Requirements

  • A Bash shell
  • Compatibility (from SKILL.md): Designed for Claude Code
  • Pre-approved tools (allowed-tools): Read, Write, Edit, Grep, Glob, Bash(api:schema-*)

Workflow steps

8 steps, taken from the first numbered list in SKILL.md.

  1. Locate all API specification files using Glob, identifying OpenAPI specs, JSON Schema definitions, and GraphQL SDL files across the project.
  2. Run structural validation to verify the specification conforms to the declared standard (OpenAPI 3.0, 3.1, or JSON Schema Draft 2020-12)…
  3. Apply Spectral linting rules to enforce naming conventions (camelCase properties, kebab-case paths), required descriptions on all…
  4. Verify schema completeness: every endpoint has documented request schemas, all response status codes have schemas (including 400, 401…
  5. Check for security scheme coverage: every endpoint either declares a security requirement or is explicitly marked as public with rationale.
  6. Detect breaking changes by comparing the current schema against the previous released version: removed endpoints, removed required fields…
  7. Validate consistency across endpoints: pagination parameters use the same naming (page/limit vs offset/count), error response envelopes…
  8. Generate a validation report with severity levels (error, warning, info) and specific file:line references for each finding.

What it can do on your machine

Read from SKILL.md and the folder at commit 80f86df. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves these tools, so the agent can use them without asking each time:

    • Read
    • Write
    • Edit
    • Grep
    • Glob
    • Bash(api:schema-*)

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Ships 1 file in scripts/ (Shell), which the agent can run.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Links to these hosts (documentation or services it may open):

    • stoplight.io
    • spec.openapis.org
    • json-schema.org
    • github.com

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

  • Compatibility

    Designed for Claude Code

    From compatibility in the SKILL.md frontmatter.

Context cost

Validating API Schemas loads about 1.3k tokens when it runs, and up to ~3.4k if it reads all its reference files. Until then it costs about 60 tokens; SKILL.md has 553 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~60
When it runs · the whole SKILL.md, loaded when a task matches
~1.3k
With references · SKILL.md plus every file in references/, read only if the agent opens them
~3.4k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); the scripts in this folder are not scanned.

SKILL.md

The full file from jeremylongshore/tons-of-skills-marketplace at commit 80f86df, republished under its MIT licence (© jeremylongshore). 553 words, ~1,336 tokens.

Download SKILL.mdSave it as .claude/skills/validating-api-schemas/SKILL.md (or your agent's skills folder). This skill also uses 4 other files; get the full folder from GitHub.
name
validating-api-schemas
description
Validate API schemas against OpenAPI, JSON Schema, and GraphQL specifications. Use when validating API schemas and contracts. Trigger with phrases like "validate API schema", "check OpenAPI spec", or "verify schema".
allowed-tools
Read, Write, Edit, Grep, Glob, Bash(api:schema-*)
compatibility
Designed for Claude Code
version
1.24.0
author
Jeremy Longshore <jeremy@intentsolutions.io>
license
MIT
tags
api, graphql, validating-api

Validating API Schemas

Overview

Validate API specifications against OpenAPI 3.0/3.1, JSON Schema Draft 2020-12, and GraphQL SDL standards using linting rules, structural analysis, and best-practice enforcement. Detect incomplete schemas, undocumented endpoints, inconsistent naming conventions, and breaking changes before they reach consumers.

Prerequisites

  • OpenAPI specification files (YAML or JSON) or GraphQL SDL schema files
  • Schema linting tool: Spectral (OpenAPI), graphql-schema-linter (GraphQL), or ajv-cli (JSON Schema)
  • Version control for schema files to enable diff-based breaking change detection
  • CI pipeline for automated schema validation on every pull request
  • oasdiff or openapi-diff for breaking change detection between versions

Instructions

  1. Locate all API specification files using Glob, identifying OpenAPI specs, JSON Schema definitions, and GraphQL SDL files across the project.
  2. Run structural validation to verify the specification conforms to the declared standard (OpenAPI 3.0, 3.1, or JSON Schema Draft 2020-12) and is syntactically valid.
  3. Apply Spectral linting rules to enforce naming conventions (camelCase properties, kebab-case paths), required descriptions on all operations, and example values for request/response schemas.
  4. Verify schema completeness: every endpoint has documented request schemas, all response status codes have schemas (including 400, 401, 404, 500), and all $ref references resolve.
  5. Check for security scheme coverage: every endpoint either declares a security requirement or is explicitly marked as public with rationale.
  6. Detect breaking changes by comparing the current schema against the previous released version: removed endpoints, removed required fields, type changes, and narrowed enum values.
  7. Validate consistency across endpoints: pagination parameters use the same naming (page/limit vs offset/count), error response envelopes follow a single standard, and date formats are consistent.
  8. Generate a validation report with severity levels (error, warning, info) and specific file:line references for each finding.

See ${CLAUDE_SKILL_DIR}/references/implementation.md for the full implementation guide.

Output

  • ${CLAUDE_SKILL_DIR}/reports/schema-validation.json - Machine-readable validation findings with severity
  • ${CLAUDE_SKILL_DIR}/reports/schema-validation.md - Human-readable report with fix recommendations
  • ${CLAUDE_SKILL_DIR}/reports/breaking-changes.md - Breaking change analysis between schema versions
  • ${CLAUDE_SKILL_DIR}/.spectral.yaml - Custom Spectral linting rule configuration
  • ${CLAUDE_SKILL_DIR}/scripts/validate-schema.sh - CI-ready schema validation script
  • ${CLAUDE_SKILL_DIR}/reports/schema-coverage.md - Endpoint documentation completeness matrix
Show full SKILL.md (229 more words)Show less

Error Handling

ErrorCauseSolution
Unresolved $refSchema references a component that does not exist or has a typoList all $ref targets and verify each resolves; check for circular references
Missing response schemaEndpoint returns undocumented status codesAdd schemas for all observed response codes; use default response as fallback
Inconsistent namingMix of camelCase and snake_case property names across endpointsDefine naming convention in Spectral ruleset; apply auto-fix where possible
Breaking change detectedRequired field added to existing request schemaMake new field optional with default value; or create new API version for breaking changes
Schema too permissiveUse of additionalProperties: true or missing type constraintsSet additionalProperties: false by default; require explicit type and format on all properties

Refer to ${CLAUDE_SKILL_DIR}/references/errors.md for comprehensive error patterns.

Examples

Pre-commit schema lint: Git pre-commit hook runs Spectral against all modified OpenAPI files, blocking commits that introduce undocumented endpoints, missing descriptions, or inconsistent naming.

Breaking change CI gate: On pull requests modifying API specs, oasdiff compares against the main branch version, failing the build if backward-incompatible changes are detected without a version bump.

Schema completeness audit: Generate a matrix showing every endpoint vs. documentation status (description, request schema, response schemas for 200/400/401/404/500, examples), highlighting gaps with coverage percentage.

See ${CLAUDE_SKILL_DIR}/references/examples.md for additional examples.

Resources

© jeremylongshore, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 4 other files (scripts, references) in skills/.curated/validating-api-schemas of jeremylongshore/tons-of-skills-marketplace.

  • SKILL.md
  • references/errors.md
  • references/examples.md
  • references/implementation.md
  • scripts/validate-schema.sh

Open the folder on GitHubat commit 80f86df

Compare with similar skills

Validating API Schemas next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Validating API Schemas compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Validating API Schemas this skilljeremylongshore/tons-of-skills-marketplace2.8k—~1.3kAutomated safety check: PassMIT
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API DesignerJeffallan/claude-skills12k1 repos~2kAutomated safety check: PassMIT
VibexRaja0sama/vibex388—~7.8kAutomated safety check: PassMIT
SpikardGoldziher/spikard123—~799Automated safety check: PassMIT
Executor Usagejeremyosih/pi-executor104—~1.4kAutomated safety check: PassMIT

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Works with

Categories

Questions about Validating API Schemas

What does Validating API Schemas do?

Validate API schemas against OpenAPI, JSON Schema, and GraphQL specifications. Validating API Schemas is an agent skill from jeremylongshore/tons-of-skills-marketplace. Validate API schemas against OpenAPI, JSON Schema, and GraphQL specifications.

When should I use Validating API Schemas?

Validating API Schemas fits situations like: validating API schemas and contracts; with phrases like validate API schema; check OpenAPI spec.

How do I install Validating API Schemas in Claude Code?

Run `npx skills add jeremylongshore/tons-of-skills-marketplace --skill validating-api-schemas -a claude-code`. Or copy the skill folder (skills/.curated/validating-api-schemas in jeremylongshore/tons-of-skills-marketplace) into .claude/skills/validating-api-schemas in your project. Claude Code loads it when a task matches its description.

How do I install Validating API Schemas in Codex?

Run `npx skills add jeremylongshore/tons-of-skills-marketplace --skill validating-api-schemas -a codex`. Or copy the skill folder (skills/.curated/validating-api-schemas in jeremylongshore/tons-of-skills-marketplace) into .agents/skills/validating-api-schemas in your project. Codex loads it when a task matches its description.

Can I use Validating API Schemas in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add jeremylongshore/tons-of-skills-marketplace --skill validating-api-schemas -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/validating-api-schemas, .gemini/skills/validating-api-schemas, .github/skills/validating-api-schemas and .opencode/skills/validating-api-schemas in your project.

What does Validating API Schemas need to run?

Going by SKILL.md and its folder, Validating API Schemas needs a shell for the scripts in its folder. Our summary lists: A Bash shell. Its frontmatter pre-approves these tools: Read, Write, Edit, Grep, Glob, Bash(api:schema-*). Compatibility (from SKILL.md): Designed for Claude Code.

Does Validating API Schemas access the network?

SKILL.md names 4 domains. As links in the text: stoplight.io, spec.openapis.org, json-schema.org and github.com. This is read from the text; nothing was executed.

Is Validating API Schemas safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. The check reads SKILL.md only: the scripts in the folder are not scanned, so read them before running anything.

What licence does Validating API Schemas use?

Validating API Schemas is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Validating API Schemas use?

About 1.3k tokens (SKILL.md is roughly 5.3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 2k tokens, read only when the agent opens those files.

What are the alternatives to Validating API Schemas?

Skills that share tags, products or a category with Validating API Schemas: Use Yaak (mountain-loop/yaak, 19k stars), API Designer (Jeffallan/claude-skills, 12k stars), Vibex (Raja0sama/vibex, 388 stars) and Spikard (Goldziher/spikard, 123 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Validating API Schemas?

jeremylongshore (a GitHub user) maintains it in jeremylongshore/tons-of-skills-marketplace, which has 2,825 GitHub stars. The repository holds 3,342 skills in this directory. The repository was last updated on October 9, 2026.

Source: jeremylongshore/tons-of-skills-marketplace on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.