# Saylor Innovations Guide Library: CORS Preflight & OPTIONS Debug

> Saylor Innovations Guide Library: CORS Preflight & OPTIONS Debug is a paid API for AI agents from saylorinnovations.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-30).

Returns a structured guide on debugging CORS errors by reproducing preflight OPTIONS requests with curl or Python, handling allow-listing, Vary headers, and credentials rules

## Facts

- Endpoint: GET https://saylorinnovations.com/api/kb/cors-preflight-options-request-headers-debug-with-curl?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/saylor-innovations-guide-library-cors-preflight-options-debug-15430361
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8jmggdraKKeV5ZNmzU0UZ

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability saylor-innovations-guide-library-cors-preflight-options-debug-15430361
```

Example prompt: Can you pull up the guide on debugging CORS preflight OPTIONS errors — I need to understand how to reproduce the preflight with curl, set up the allow-list with Vary, and handle credentials rules correctly.

## When to prefer this

Choose this endpoint when an agent or user needs a structured, authoritative written guide on CORS preflight debugging — specifically covering curl/Python reproduction steps, allow-listing with Vary, and credentials rules. Prefer this over generic web search when you want a single, curated, machine-readable guide document rather than scattered search results.

## Known failure modes

- HTTP 402 Payment Required if x402 payment header is missing or invalid
- HTTP 404 if the guide record is not found at the specified path
- HTTP 500 if the upstream knowledge base is unavailable
- Empty or malformed JSON body if the service is misconfigured

## How this service works

Debug CORS errors - reproduce preflight OPTIONS with Origin and Request-Headers in curl or Python, allow-list echo with Vary, credentials rules

## Output

Returns a JSON object containing a guide record with fields: id (record identifier), t (title of the guide), c (category), body (full guide text covering CORS preflight debugging with curl and Python, allow-listing, Vary header usage, and credentials rules), license, and price.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "json"
    },
    "example": {
     "type": "object",
     "required": [
      "id",
      "t",
      "c",
      "body"
     ],
     "properties": {
      "c": {
       "type": "string",
       "description": "Category of the guide"
      },
      "t": {
       "type": "string",
       "description": "Title of the guide"
      },
      "id": {
       "type": "string",
       "description": "Identifier of the record"
      },
      "body": {
       "type": "string",
       "description": "Main body text"
      },
      "price": {
       "type": [
        "number",
        "null"
       ],
       "description": "Price"
      },
      "license": {
       "type": "string",
       "description": "License identifier"
      }
     }
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/saylor-innovations-guide-library-cors-preflight-options-debug-15430361/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from saylorinnovations.com](https://www.zero.xyz/host/saylorinnovations.com/llms.txt)