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 agentmods add skills/jeet129/praxis/api-designnpx skills add jeet129/praxis --skill api-designgit clone --depth 1 https://github.com/jeet129/praxisWrote 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/jeet129/praxis/api-design)<a href="https://agentmods.dev/skills/jeet129/praxis/api-design"><img src="https://agentmods.dev/badge/skills/jeet129/praxis/api-design.svg" alt="Measured on agentmods" 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 | $0.00122 | $0.02898 |
| Opus 5 | $0.00061 | $0.01449 |
| Sonnet 5 | $0.00024 | $0.00580 |
| Haiku 4.5 | $0.00012 | $0.00290 |
Grade A, and why
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 — 236 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Design
capability: architecture
domain: backend
state: active
dependencies:
- engineering-standards
- requirements-elicitation
- nfr-definition
triggers:
- "introducing a new API endpoint, RPC, or event topic"
- "extending an existing API contract"
- "versioning or deprecating an existing API"
- "defining a webhook contract"
- "designing a public API surface"
outputs:
- OpenAPI/Proto/AsyncAPI specification file
- versioning policy
- deprecation policy
- pagination/filtering/sorting conventions
- idempotency strategy per mutation
- error model (error codes, shape, examples)
consumers:
- backend-developer (implements against the spec)
- frontend-developer (consumes the spec for client code)
- code-review (checks code against the spec)
- api-documentation generators
references:
- rest-openapi.md
- grpc-proto.md
- asyncapi-events.md
- graphql.md
- contract-review.md
Contract-first. The specification is written before implementation begins, reviewed (by the Architecture Challenger and the consuming agent), and locked. The implementation is then a faithful realization of the contract; deviations are caught at code review against the spec.
Reviewing a whole contract baseline (not a single endpoint) — e.g. a surface the SA generated in bulk, possibly after architecture_sign_off — use references/contract-review.md. It is the checklist behind the /review contracts command and covers shared-foundation consistency, evolvability/versioning, REST/gRPC/event hygiene, and the safety/privacy surfaces. Generation is not review: a baseline must be vetted by a different role before slices consume it.
This is one of the highest-leverage skills in the library — APIs that ship without contract-first design accumulate inconsistencies, get redesigned a quarter later, and break consumers in the meantime.
When this skill fires
- A slice introduces a new endpoint, RPC, event topic, or webhook.
- An existing contract needs to be extended (new field, new operation).
- A breaking change is being considered (triggers the versioning + deprecation policy).
- A client (frontend, mobile, partner) needs the contract before they can plan their work.
What ships with it
2 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.
- 4d ago First seen · 236 lines · 122 tokens per session scan A 9eb628802219
api-design is a skill published in the GitHub repository jeet129/praxis (7 stars, last pushed yesterday), licensed MIT. It adds 122 tokens to every session and 2,898 once invoked, about $0.0006 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.
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