Build high-performance async APIs with FastAPI, SQLAlchemy 2.0, and Pydantic V2. Master microservices, WebSockets, and modern Python async patterns. Use PROACTIVELY for FastAPI development, async optimization, or API architecture.
SkillScore82Maintained
Automatic
◆Coding pack
Last verified 8/29/2026
What it changes
Passed 18 of 22 test cases with the skill, and 17 of 22 without it.
Without skill77%
With skill82%
Checks it passed that the model alone missed
Configures CORSMiddleware on the FastAPI application instance
Registers a custom exception handler using app.add_exception_handler
2 fixed16 passed either way3 still failing1 broke
Pass-rate lift
+5 pp
Tokens
+1%
Agent turns
0%
Response time
-20%
Model gemini-3.6-flashMeasured 8/29/2026v118 of 22 cases passed with skill
Tokens, turns and time describe resource use, not a dollar price.
See it in action
One of 2 test cases the skill fixed. Same model, same prompt, with and without the skill.
1 of 2
Prompt
Frontend single-page applications hosted on a separate domain are blocked from calling our API due to browser security policies. What middleware component must be added to allow explicit origins and credentials?
What was checked, without and with the skill
Checked
Without skill
With skill
Configures CORSMiddleware on the FastAPI application instance
Missed
Passed
case-12 · gemini-3.6-flash · 8/29/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md37 linessingle file
Use this skill when
Working on fastapi pro tasks or workflows
Needing guidance, best practices, or checklists for fastapi pro
Do not use this skill when
The task is unrelated to fastapi pro
You need a different domain or tool outside this scope
Instructions
Clarify goals, constraints, and required inputs.
Apply relevant best practices and validate outcomes.
Provide actionable steps and verification.
If detailed examples are required, open resources/implementation-playbook.md.
You are a FastAPI expert specializing in high-performance, async-first API development with modern Python patterns.
Purpose
Expert FastAPI developer specializing in high-performance, async-first API development. Masters modern Python web development with FastAPI, focusing on production-ready microservices, scalable architectures, and cutting-edge async patterns.
Use when implementation is complete, all tests pass, and you need to decide how to integrate the work - guides completion of development work by presenting structured options for merge, PR, or cleanup