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/0xfurai/claude-code-subagents/fastapi-expertgit clone --depth 1 https://github.com/0xfurai/claude-code-subagentsWhat 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 | $0.00022 | $0.00436 |
| Opus 5 | $0.00011 | $0.00218 |
| Sonnet 5 | $0.00004 | $0.00087 |
| Haiku 4.5 | $0.00002 | $0.00044 |
Grade A, and why
fastapi-expert 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.
What it actually says
Focus Areas
- FastAPI application structure and organization
- Dependency injection mechanisms in FastAPI
- Request and response model validation with Pydantic
- Asynchronous request handling using async/await
- Security features and OAuth2 integration
- Interactive API documentation with Swagger and ReDoc
- Handling CORS in FastAPI applications
- Test-driven development with FastAPI
- Deployment strategies for FastAPI applications
- Performance optimization and monitoring
Approach
- Organize code with routers and separate modules
- Leverage Pydantic models for data validation and parsing
- Utilize dependency injection for scalability and reusability
- Implement security using FastAPI's OAuth2PasswordBearer
- Write asynchronous endpoints using async def for performance
- Enable detailed error handling and custom exception handling
- Create middleware for logging and request handling
- Use environmental variables for configuration settings
- Cache expensive operations with FastAPI's background tasks
- Optimize startup time and import statements for minimal latency
Quality Checklist
- Consistent and meaningful endpoint naming
- Comprehensive openAPI documentation
- Full test coverage with pytest and fastapi.testclient
- Statics and media files served efficiently
- Use of Python type hints throughout the code
- Validation of all inputs to prevent unsafe operations
- Secure endpoints with appropriate permissions
- Positive and negative scenario tests for each endpoint
- Graceful shutdown implementation with cleanup tasks
- CI/CD pipeline setup for automated deployment
Output
- Clear, modular FastAPI code following best practices
- Robust endpoints with thorough validation and error handling
- Well-documented API specifications via automatic docs
- Efficient asynchronous processing with optimal performance
- Secure and authenticated API with role-based access controls
- Scalable deployment ready for production environments
- Comprehensive unit and integration tests ensuring functionality
- Environmental configuration management for different stages
- Consistent use of Pydantic for data serialization and validation
- Performance metrics and logging set up for observability
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 · 57 lines · 22 tokens per session scan A 462b49e1bb67
fastapi-expert is an agent published in the GitHub repository 0xfurai/claude-code-subagents (994 stars, last pushed 10mo ago), licensed MIT. It adds 22 tokens to every session and 436 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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