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 vasilyu1983/AI-Agents-public --skill dev-api-designgit clone --depth 1 https://github.com/vasilyu1983/AI-Agents-publicWrote 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/vasilyu1983/ai-agents-public/dev-api-design)<a href="https://agentmods.dev/skills/vasilyu1983/ai-agents-public/dev-api-design"><img src="https://agentmods.dev/badge/skills/vasilyu1983/ai-agents-public/dev-api-design.svg" alt="Measured on agentmods" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00044 | $0.03509 |
| Opus 5 | $0.00022 | $0.01754 |
| Sonnet 5 | $0.00009 | $0.00702 |
| Haiku 4.5 | $0.00004 | $0.00351 |
Grade A, and why
dev-api-design 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 4d 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 — 171 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Design
Use this skill for contract-first API design across REST, GraphQL, gRPC, tRPC, AsyncAPI, and agent-facing interfaces. It owns contract choice, auth boundaries, versioning, errors, pagination, rate limits, idempotency, and validation; it does not replace backend implementation or security review.
Style Decision Table
| API style | Choose when | Avoid when | Canonical artifact |
|---|---|---|---|
| REST + OpenAPI | Public APIs, broad tooling compatibility, cacheable resources | Sub-10ms internal calls, streaming-first | OpenAPI 3.2.0 |
| GraphQL | Complex client-driven query shapes, multi-team schema ownership | Simple CRUD, caching is critical, single-team | GraphQL SDL |
| gRPC | Internal services, bidirectional streaming, type-critical boundaries | Public internet consumers, browser-native clients | protobuf |
| tRPC | TypeScript monorepos with shared server+client | Non-TS stacks, public third-party consumers | TypeScript types |
| AsyncAPI + webhooks | Event-driven contracts, pub/sub, push notifications | Synchronous request-reply | AsyncAPI 3.x |
| MCP tool layer | Agent or LLM is the primary consumer | Human-only clients | MCP tool schema |
Quick Reference
| API style | Load |
|---|---|
| REST + OpenAPI | references/restful-design-patterns.md, references/openapi-guide.md |
| GraphQL | references/graphql-patterns.md |
| gRPC | references/grpc-patterns.md |
| tRPC | references/trpc-patterns.md |
| AsyncAPI and webhooks | references/asyncapi-patterns.md, references/webhook-patterns.md |
| Core cross-cutting | references/error-handling-patterns.md, references/authentication-patterns.md, references/pagination-filtering.md, references/rate-limiting-patterns.md, references/api-testing-patterns.md |
What ships with it
34 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.
- agents/openai.yaml 382 B
- assets/cross-platform/api-patterns-universal.md 17 KB
- assets/cross-platform/template-api-design-review-checklist.md 4.3 KB
- assets/cross-platform/template-api-error-model.md 3.7 KB
- assets/cross-platform/template-api-governance.md 9.6 KB
- assets/django-rest/django-rest-complete-api.md 13 KB
- assets/express-nodejs/express-complete-api.md 24 KB
- assets/fastapi/fastapi-complete-api.md 24 KB
- assets/oasdiff-ci.yml 1.2 KB
- assets/openapi-template.yaml 12 KB
- assets/spectral-ruleset.yaml 3.7 KB
- assets/spring-boot/spring-boot-complete-api.md 21 KB
- data/sources.json 12 KB
- data/versions.json 2.3 KB
- learnings.consolidated.md 590 B
- learnings.md 360 B
- references/api-design-best-practices.md 20 KB
- references/api-security-checklist.md 18 KB
- references/api-testing-patterns.md 14 KB
- references/asyncapi-patterns.md 2.8 KB
- references/authentication-patterns.md 16 KB
- references/error-handling-patterns.md 16 KB
- references/graphql-patterns.md 18 KB
- references/grpc-patterns.md 4.3 KB
- references/llm-agent-api-contracts.md 11 KB
- references/openapi-32-arazzo-101.md 3.0 KB
- references/openapi-guide.md 22 KB
- references/pagination-filtering.md 15 KB
- references/rate-limiting-patterns.md 16 KB
- references/real-time-api-patterns.md 15 KB
- references/restful-design-patterns.md 14 KB
- references/trpc-patterns.md 11 KB
- references/versioning-strategies.md 14 KB
- references/webhook-patterns.md 12 KB
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.
- 4d ago Changed ed201a53266c
- 8d ago First seen · 171 lines · 44 tokens per session scan A b56af437dcd2
dev-api-design is a skill published in the GitHub repository vasilyu1983/AI-Agents-public (86 stars, last pushed 5d ago), licensed MIT. It adds 44 tokens to every session and 3,509 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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