api

A feature-planning tool that defines how software parts communicate. For web services it creates an OpenAPI document, a standard description of HTTP endpoints, and it can also describe other interfaces such as command-line tools, libraries, or events.

In plain words
What is it for?
Use it to derive and check an API or other public interface from a feature's requirements, data model, and user flows.
Why use it?
It reduces disagreements between frontend, backend, and other systems by recording the expected inputs, outputs, and errors in one contract.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/genkovich/sdd/api
Any agent
npx skills add genkovich/sdd --skill api
Clone the repo
git clone --depth 1 https://github.com/genkovich/sdd

Made for: Claude Code, Codex.

Per session 220 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,247 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00220 $0.04247
Opus 5 $0.00110 $0.02124
Sonnet 5 $0.00044 $0.00849
Haiku 4.5 $0.00022 $0.00425

Measured 2d ago against content hash cdf9d3851121, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade C, and why

api scanned grade C with 1 finding 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 2d 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.

Tells the agent never to refusehighAnti-refusal

Suppressing the ability to decline removes a core safety control; a later harmful request then succeeds.

**Determine the interface kind — read `sad.md` frontmatter `target_surfaces` FIRST** (design already declared it; the surface picks the contract form per [`../_shared/surfaces.md`](../_shared/surfaces.md): `backend-servi
skills/api/SKILL.md · 99 lines

How it starts

The opening of the file, as written. The whole thing — 99 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill: api

Projects the upstream artifacts into one interface contract. By default that's an HTTP/OpenAPI contract; this skill is interface-kind aware — and the kind comes from the surface(s) design declared in sad.md frontmatter target_surfaces, read here, not re-derived (→ ../_shared/surfaces.md). For a non-HTTP project it produces the matching contract form (or steps aside):

  • HTTP / REST (default) → contracts/openapi.yaml (OpenAPI 3.1) + api-sync-report.md.
  • gRPC / RPC → a .proto (or the repo's IDL) with the same derive-and-drift discipline.
  • CLIcontracts/cli.md — the command/flag/exit-code surface derived from the AC.
  • Library / SDKcontracts/public-api.md — the public signatures/types the feature exposes.
  • Event-only / worker → just contracts/events.md (no request/response surface).
  • No external interface (pure internal logic) → skip with a one-line note in the report; go straight to tasks.

Whatever the form, the contract is derived from data-model.md — or, on a legal no-schema-change skip, the existing schema — plus the sad.md §6 sequences + the spec's AC, never typed by hand — generation that diverges from the model or the sequences is the bug this skill exists to catch. The rest of this file details the HTTP path (the common case); the same derive → drift-check → reconcile loop applies to the other forms with the form-appropriate artifact.

This skill keeps only its own machinery. Question phrasing is shared../_shared/ask-style.md. Depth (events doc only when async; one resource vs full surface) follows the size matrix../_shared/size-matrix.md. The drift-resolution dialog reuses the shared 4-state actions — keep it short, point the machinery to _shared.

Contract summary/description prose follows artifact_language — paths, operationId, status codes and schema names never translate → ../_shared/artifact-language.md.

Read the full file on GitHub · 99 lines

Files

What ships with it

3 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.

Changes

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.

  1. 2d ago First seen · 99 lines · 220 tokens per session scan C cdf9d3851121

Subscribe to this mod's changes

api is a skill published in the GitHub repository genkovich/sdd (118 stars, last pushed 13d ago), licensed MIT. It adds 220 tokens to every session and 4,247 once invoked, about $0.0011 per session on Opus 5. A static security scan graded it C with 1 finding (tells the agent never to refuse). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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