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 ancoleman/ai-design-components --skill designing-apisgit clone --depth 1 https://github.com/ancoleman/ai-design-componentsWrote 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/ancoleman/ai-design-components/designing-apis)<a href="https://agentmods.dev/skills/ancoleman/ai-design-components/designing-apis"><img src="https://agentmods.dev/badge/skills/ancoleman/ai-design-components/designing-apis/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/ancoleman/ai-design-components/designing-apis"><img src="https://agentmods.dev/badge/skills/ancoleman/ai-design-components/designing-apis.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00045 | $0.02554 |
| Opus 5 | $0.00023 | $0.01277 |
| Sonnet 5 | $0.00009 | $0.00511 |
| Haiku 4.5 | $0.00005 | $0.00255 |
Grade A, and why
designing-apis 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.
How it starts
The opening of the file, as written. The whole thing — 402 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Designing APIs
Design well-structured, scalable APIs using REST, GraphQL, or event-driven patterns. Focus on resource design, versioning, error handling, pagination, rate limiting, and security.
When to Use This Skill
Use when:
- Designing a new REST, GraphQL, or event-driven API
- Establishing API design standards for a team or organization
- Choosing between REST, GraphQL, WebSockets, or message queues
- Planning API versioning and breaking change management
- Defining error response formats and HTTP status code usage
- Implementing pagination, filtering, and rate limiting patterns
- Designing OAuth2 flows or API key authentication
- Creating OpenAPI or AsyncAPI specifications
Do NOT use for:
- Implementation code (use
api-patternsskill for Express, FastAPI code) - Authentication implementation (use
auth-securityskill for JWT, sessions) - API testing strategies (use
testing-strategiesskill) - API deployment and infrastructure (use
deploying-applicationsskill)
Core Design Principles
Resource-Oriented Design (REST)
Use nouns for resources, not verbs in URLs:
✓ GET /users List users
✓ GET /users/123 Get user 123
✓ POST /users Create user
✓ PATCH /users/123 Update user 123
✓ DELETE /users/123 Delete user 123
✗ GET /getUsers
✗ POST /createUser
Nest resources for relationships (limit depth to 2-3 levels):
✓ GET /users/123/posts
✓ GET /users/123/posts/456/comments
✗ GET /users/123/posts/456/comments/789/replies (too deep)
For complete REST patterns, see references/rest-design.md
HTTP Method Semantics
| Method | Idempotent | Safe | Use For | Success Status |
|---|---|---|---|---|
| GET | Yes | Yes | Read resource | 200 OK |
| POST | No | No | Create resource | 201 Created |
| PUT | Yes | No | Replace entire resource | 200 OK, 204 No Content |
| PATCH | No | No | Update specific fields | 200 OK, 204 No Content |
| DELETE | Yes | No | Remove resource | 204 No Content, 200 OK |
What ships with it
12 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.
- examples/asyncapi/order-events.yaml 2.5 KB
- examples/graphql/schema.graphql 1.6 KB
- outputs.yaml 10 KB
- references/authentication.md 10 KB
- references/error-handling.md 10 KB
- references/graphql-design.md 6.0 KB
- references/pagination-patterns.md 4.9 KB
- references/protocol-selection.md 6.7 KB
- references/rate-limiting.md 6.7 KB
- references/rest-design.md 13 KB
- references/versioning-strategies.md 13 KB
- scripts/validate-openapi.sh 581 B runs code
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 · 402 lines · 45 tokens per session scan A 8474e7e1d019
designing-apis is a skill published in the GitHub repository ancoleman/ai-design-components (519 stars, last pushed 9mo ago), licensed MIT. It adds 45 tokens to every session and 2,554 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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