API Documentation Writer
Converts an endpoint description or code snippet into clean, developer-ready API documentation with parameters, examples, and error codes.
API Documentation Writer is a free AI skill for docs & knowledge bases. Converts an endpoint description or code snippet into clean, developer-ready API documentation with parameters, examples, and error codes. It works with Claude, ChatGPT, Cursor and is ready to use out of the box.
About this skill
API Documentation Writer takes a rough description of an API endpoint — or the actual route handler code — and produces polished, standardized documentation: endpoint summary, request parameters, example request/response, and possible error codes with explanations. It follows conventions familiar from documentation like Stripe's or Twilio's, so the output is immediately usable in a developer portal. Built for backend engineers and API teams who need consistent docs without hand-formatting every endpoint.
What it does
Given an endpoint description or code snippet, the skill outputs a full documentation entry: summary, HTTP method/path, parameters table, example request, example response, and error code reference.
What is included
- Endpoint summary and method/path
- Parameters table (name, type, required, description)
- Example request (with realistic sample values)
- Example response (success case)
- Error code reference table
How to use it
1. Download the SKILL.md file 2. Upload it to a new Claude conversation 3. Paste an endpoint description or the route handler code 4. Receive complete, developer-ready documentation
Examples
POST /api/v1/subscriptions - creates a new subscription for a customer. Takes customer_id, plan_id, and optional coupon_code. Returns the subscription object. Fails if customer or plan doesn't exist, or coupon is invalid/expired.
## Create Subscription
`POST /api/v1/subscriptions`
Creates a new subscription for a customer on a specified plan.
### Parameters
| Name | Type | Required | Description |
|------|------|----------|-------------|
| customer_id | string | Yes | The unique identifier of the customer |
| plan_id | string | Yes | The unique identifier of the subscription plan |
| coupon_code | string | No | Optional coupon code to apply a discount |
### Example Request
```json
POST /api/v1/subscriptions
{
"customer_id": "cus_8f92a1",
"plan_id": "plan_pro_monthly",
"coupon_code": "WELCOME10"
}
```
### Example Response
```json
{
"id": "sub_3d81ff",
"customer_id": "cus_8f92a1",
"plan_id": "plan_pro_monthly",
"status": "active",
"created_at": "2026-07-11T10:00:00Z"
}
```
### Error Codes
| Code | Meaning |
|------|---------|
| 404 | Customer or plan not found |
| 422 | Coupon code invalid or expired |
| 400 | Missing required parameter |FAQ
What is this skill for?
How do I install it?
Can it read actual route handler code?
What documentation style does it follow?
How is this different from auto-generated docs from OpenAPI/Swagger?
Can it document an entire API with many endpoints at once?
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