claude-skills is a collection of specialized skills that extends Claude Code for full-stack development. Developers use it for programming languages, frameworks, infrastructure, APIs, testing, DevOps, security, data and machine learning, platform tasks, and project workflows.
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.
npx skills add Jeffallan/claude-skills --skill api-designergit clone --depth 1 https://github.com/Jeffallan/claude-skillsWrote 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/jeffallan/claude-skills/api-designer)<a href="https://agentmods.dev/skills/jeffallan/claude-skills/api-designer"><img src="https://agentmods.dev/badge/skills/jeffallan/claude-skills/api-designer/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.
<a href="https://agentmods.dev/skills/jeffallan/claude-skills/api-designer"><img src="https://agentmods.dev/badge/skills/jeffallan/claude-skills/api-designer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector warn
SkillSpector: 5 findings, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium MCP Rug Pull · line 25 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 213 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 26 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium Data Exfiltration · line 143 Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
- medium Data Exfiltration · line 187 Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
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 | $0.00039 | $0.01849 |
| Opus 5 | $0.00019 | $0.00924 |
| Sonnet 5 | $0.00008 | $0.00370 |
| Haiku 4.5 | $0.00004 | $0.00185 |
Grade A, and why
api-designer 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 9d 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.
Copies of this mod
2 near-identical copies found in the catalogue:
- api-designer — 94% identical, 2 lines differ
- api-designer — 94% identical, 2 lines differ
How it starts
The opening of the file, as written. The whole thing — 220 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Designer
Senior API architect specializing in REST and GraphQL APIs with comprehensive OpenAPI 3.1 specifications.
Core Workflow
- Analyze domain — Understand business requirements, data models, and client needs
- Model resources — Identify resources, relationships, and operations; sketch entity diagram before writing any spec
- Design endpoints — Define URI patterns, HTTP methods, request/response schemas
- Specify contract — Create OpenAPI 3.1 spec; validate before proceeding:
npx @redocly/cli lint openapi.yaml - Mock and verify — Spin up a mock server to test contracts:
npx @stoplight/prism-cli mock openapi.yaml - Plan evolution — Design versioning, deprecation, and backward-compatibility strategy
Reference Guide
Load detailed guidance based on context:
| Topic | Reference | Load When |
|---|---|---|
| REST Patterns | references/rest-patterns.md |
Resource design, HTTP methods, HATEOAS |
| Versioning | references/versioning.md |
API versions, deprecation, breaking changes |
| Pagination | references/pagination.md |
Cursor, offset, keyset pagination |
| Error Handling | references/error-handling.md |
Error responses, RFC 7807, status codes |
| OpenAPI | references/openapi.md |
OpenAPI 3.1, documentation, code generation |
Constraints
MUST DO
- Follow REST principles (resource-oriented, proper HTTP methods)
- Use consistent naming conventions (snake_case or camelCase — pick one, apply everywhere)
- Include comprehensive OpenAPI 3.1 specification
- Design proper error responses with actionable messages (RFC 7807)
- Implement pagination for all collection endpoints
- Version APIs with clear deprecation policies
- Document authentication and authorization
- Provide request/response examples
MUST NOT DO
- Use verbs in resource URIs (use
/users/{id}, not/getUser/{id}) - Return inconsistent response structures
- Skip error code documentation
- Ignore HTTP status code semantics
- Design APIs without a versioning strategy
- Expose implementation details in the API surface
- Create breaking changes without a migration path
- Omit rate limiting considerations
What ships with it
5 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.
- 9d ago First seen · 220 lines · 39 tokens per session scan A 75a1d0df1264
api-designer is a skill published in the GitHub repository Jeffallan/claude-skills (11,380 stars, last pushed 1mo ago), licensed MIT. It adds 39 tokens to every session and 1,849 once invoked, about $0.0002 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.
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