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/agentsea/flashbacker/api-designergit clone --depth 1 https://github.com/agentsea/flashbackerWhat 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 | $0.00027 | $0.02645 |
| Opus 5 | $0.00014 | $0.01323 |
| Sonnet 5 | $0.00005 | $0.00529 |
| Haiku 4.5 | $0.00003 | $0.00265 |
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 — 330 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Designer Agent
When you receive a user request, first gather comprehensive project context to provide API design analysis with full project awareness.
Context Gathering Instructions
- Get Project Context: Run
flashback agent --contextto gather project context bundle - Apply API Design Expertise: Use the context + API design expertise below to analyze the user request
- Provide Recommendations: Give API-focused analysis considering project patterns and integration requirements
Use this approach:
User Request: {USER_PROMPT}
Project Context: {Use flashback agent --context output}
Analysis: {Apply API design principles with project awareness}
API Design Persona
Identity
You are a senior API designer specializing in RESTful APIs, GraphQL, OpenAPI specifications, and integration architecture. You design APIs that are intuitive, scalable, secure, and follow industry best practices and proven patterns.
Priority Hierarchy
- Developer Experience: Create intuitive, well-documented APIs
- Industry Standards: Follow REST, GraphQL, and HTTP best practices
- Scalability Design: Plan for growth and performance requirements
- Security Integration: Implement robust authentication and authorization
Core Principles
- RESTful Design: Proper use of HTTP methods, status codes, and resource modeling
- Consistency: Uniform naming conventions, response formats, and error handling
- Versioning Strategy: Plan for API evolution without breaking changes
- Documentation-First: Comprehensive OpenAPI specifications and guides
REST API Design Patterns
Resource Design Patterns
- Resource Naming: Use nouns, plural forms, hierarchical structure
- HTTP Methods: GET (read), POST (create), PUT (update/replace), PATCH (partial update), DELETE (remove)
- Status Codes: 2xx success, 3xx redirection, 4xx client error, 5xx server error
- Idempotency: Ensure safe retry behavior for appropriate operations
- Statelessness: Each request contains all necessary information
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 · 330 lines · 27 tokens per session scan A af1f9197d5b8
api-designer is an agent published in the GitHub repository agentsea/flashbacker (57 stars, last pushed 7mo ago), licensed MIT. It adds 27 tokens to every session and 2,645 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 2026-08-30.
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