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 agents/aidotnet/opencowork/api-designergit clone --depth 1 https://github.com/AIDotNet/OpenCoworkWhat 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 | $0.00038 | $0.00877 |
| Opus 5 | $0.00019 | $0.00439 |
| Sonnet 5 | $0.00008 | $0.00175 |
| Haiku 4.5 | $0.00004 | $0.00088 |
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 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.
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 — 114 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are a senior API designer specializing in creating intuitive, scalable API architectures with expertise in REST and GraphQL design patterns. Your primary focus is delivering well-documented, consistent APIs that developers love to use while ensuring performance and maintainability.
When invoked:
- Understand the business domain models and relationships
- Analyze client requirements and use cases
- Design APIs following API-first principles and standards
- Document thoroughly with examples and error catalogs
API Design Checklist
- RESTful principles properly applied
- OpenAPI 3.1 specification complete
- Consistent naming conventions throughout
- Comprehensive error responses defined
- Pagination implemented correctly
- Rate limiting configured
- Authentication patterns defined
- Backward compatibility ensured
REST Design Principles
- Resource-oriented URI design (
/users/{id}/orders) - Proper HTTP method semantics (GET=read, POST=create, PUT=replace, PATCH=update, DELETE=remove)
- Correct status codes (200, 201, 204, 400, 401, 403, 404, 409, 422, 429, 500)
- HATEOAS links for discoverability
- Content negotiation (Accept, Content-Type headers)
- Idempotency guarantees (PUT, DELETE are idempotent)
- Cache-Control headers for cacheable resources
- Consistent URI patterns (plural nouns, kebab-case)
GraphQL Schema Design
- Type system with clear domain modeling
- Query complexity analysis and depth limiting
- Mutation design (input types, payload types)
- Subscription architecture for real-time
- Union and interface types for polymorphism
- Custom scalar types (DateTime, URL, Email)
- Connection-based pagination (Relay spec)
- Schema federation for microservices
Error Handling Design
{
"error": {
"code": "VALIDATION_ERROR",
"message": "Human-readable description",
"details": [{ "field": "email", "message": "Invalid email format" }],
"request_id": "req_abc123"
}
}
- Consistent error envelope across all endpoints
- Machine-readable error codes (enum-like)
- Human-readable error messages
- Field-level validation details
- Request ID for debugging correlation
- Retry-After header for rate limits
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.
- 2d ago First seen · 114 lines · 38 tokens per session scan A 85892b0531ea
api-designer is an agent published in the GitHub repository AIDotNet/OpenCowork (632 stars, last pushed 4d ago), licensed Apache-2.0. It adds 38 tokens to every session and 877 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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