# Substack Category Feed

> Substack Category Feed is a paid API for AI agents from x402.apidirect.io, paid per call via x402, $0.004/call, status unknown (last checked 2026-10-30).

Fetches the posts and notes feed for a specific Substack category, sortable by top, most recent, or posts only.

## Facts

- Endpoint: GET https://x402.apidirect.io/v1/substack/category/feed?utm_source=zero.xyz
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/substack-category-feed-afac3d68
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_GM6KBnpAO17ZUEBoKCQBA

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 substack-category-feed-afac3d68
```

Example prompt: Pull the top posts from Substack's technology category — fetch 3 pages sorted by top so I can see what's performing best there.

## When to prefer this

Use this endpoint when you need structured access to Substack's category-level feed — browsing topic areas like technology, finance, or politics — rather than searching by keyword or fetching a specific publication. It's ideal for content discovery, competitive research, or monitoring what's popular or new within a Substack topic vertical. Prefer it over the trending endpoint when you want category-specific rather than platform-wide content.

## Known failure modes

- Invalid or unrecognized category slug/ID returns an error or empty feed
- Pages parameter out of range (below 1 or above 250) triggers validation error
- Network or upstream Substack availability issues may cause partial results or timeout
- Early stop when category has fewer items than requested pages

## How this service works

Get a Substack category's feed: the posts and notes Substack shows for the topic, top, newest or posts only.

## Output

Returns a merged list of feed items (posts and/or notes) from the specified Substack category, up to 11 items per page. Each item includes post or note details as surfaced on Substack's category explore page, such as title, author, publication, and engagement signals. Multiple pages are merged into a single response.

## 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",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "category"
     ],
     "properties": {
      "pages": {
       "type": "integer",
       "default": 1,
       "maximum": 250,
       "minimum": 1,
       "description": "Number of pages to fetch and merge into one response (1-250, billed per page returned). Each page returns about 11 items. Fetching stops early when there are no more results."
      },
      "sort_by": {
       "enum": [
        "top",
        "most_recent",
        "posts"
       ],
       "type": "string",
       "default": "top",
       "description": "Sort order: top, most_recent or posts (posts only, no notes)"
      },
      "category": {
       "type": "string",
       "maxLength": 100,
       "description": "Category ID or slug, e.g. 4 or technology. See Category IDs (https://apidirect.io/docs/substack-category-ids)"
      }
     }
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/substack-category-feed-afac3d68/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402.apidirect.io](https://www.zero.xyz/host/x402.apidirect.io/llms.txt)