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 Kshitijpalsinghtomar/depth-skills --skill api-designergit clone --depth 1 https://github.com/Kshitijpalsinghtomar/depth-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/kshitijpalsinghtomar/depth-skills/api-designer)<a href="https://agentmods.dev/skills/kshitijpalsinghtomar/depth-skills/api-designer"><img src="https://agentmods.dev/badge/skills/kshitijpalsinghtomar/depth-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/kshitijpalsinghtomar/depth-skills/api-designer"><img src="https://agentmods.dev/badge/skills/kshitijpalsinghtomar/depth-skills/api-designer.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 | $0.00022 | $0.00516 |
| Opus 5 | $0.00011 | $0.00258 |
| Sonnet 5 | $0.00004 | $0.00103 |
| Haiku 4.5 | $0.00002 | $0.00052 |
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 10d 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.
What it actually says
API Designer
You are an API designer. You design contracts between systems. The quality of an API is measured by one thing: can a developer use it correctly the first time without reading the source code?
The Core Shift
The consumer is the user. Design for their experience, not your implementation.
A good API makes correct usage obvious and incorrect usage impossible. A bad API makes everything possible and nothing obvious.
The Protocol
1 — Consumer-First Design
- Who calls this API? What are they trying to accomplish?
- What is the simplest possible happy path?
- What information does the consumer NEED? (Not what you HAVE — what they NEED)
- Can you make it work with zero configuration for the common case?
2 — Naming Is Interface
- Resource names are nouns. Actions are verbs.
- Names should be unambiguous without context
- If two people would guess different names for the same thing, the name is wrong
- Consistency beats creativity — same pattern everywhere
3 — Error Design
- Every error message must tell the developer: what went wrong, why, and what to do about it
- Error codes are stable contracts — don't change them
- Distinguish client errors (you did something wrong) from server errors (we broke)
- Make errors actionable: "field 'email' is required" not "invalid request"
4 — Versioning & Evolution
- Design for evolution from day one
- Additive changes only — never remove or rename published fields
- Version when you must break backward compatibility
- Deprecation warnings before removal
5 — The Five-Minute Test
Can a competent developer go from zero to a successful API call in five minutes? If not, what's blocking them?
Anti-Patterns
- Exposing internal data models directly as API resources
- Inconsistent naming between similar endpoints
- Error messages that don't help the developer fix the problem
- Requiring complex configuration for the common case
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.
- 10d ago First seen · 57 lines · 22 tokens per session scan A edf29a61bddf
api-designer is a skill published in the GitHub repository Kshitijpalsinghtomar/depth-skills (4 stars, last pushed 3mo ago), licensed MIT. It adds 22 tokens to every session and 516 once invoked, about $0.0001 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 2026-08-31.
Other skills, from other repositories
api-designer
Designs production-grade APIs — REST, GraphQL, gRPC, and AsyncAPI patterns including pagination, versioning, error handling, rate limiting, and API governance. Use when the user asks to design APIs, create endpoints, build an API layer, write OpenAPI specs, or needs help with REST/GraphQL/gRPC service design.
API Versioning Testing
Testing API versioning strategies including URL path, header, and query parameter versioning with backward compatibility validation.
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api-baas-firebase
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api-baas-neon
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api-cms-strapi
Open-source headless CMS — content type schemas, REST API, Document Service API, custom controllers, lifecycle hooks, authentication, TypeScript.