# API Direct – Search Substack Publications

> API Direct – Search Substack Publications 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).

Search Substack publications by name or keyword, with optional language and pagination filters.

## Facts

- Endpoint: GET https://x402.apidirect.io/v1/substack/publications?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/api-direct-search-substack-publications-bc45aeab
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_gESWRSKm9Cnv-kd5y12yp

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 api-direct-search-substack-publications-bc45aeab
```

Example prompt: Search Substack for publications about personal finance and return the first page of results.

## When to prefer this

Use this endpoint when you need to discover or search for Substack publications by topic or name, especially when you want paginated browsing or language-ranked results. Prefer this over manually scraping Substack or using generic web search when you need structured publication metadata.

## Known failure modes

- Empty results if the keyword matches no publications
- Pagination out of range if page > 4 is requested
- Query too long if keyword exceeds 500 characters
- Invalid language code if not a valid 2-letter ISO code

## How this service works

Search Substack publications by name or keyword.

## Output

Returns a paginated list of Substack publications matching the search query, including publication names, descriptions, and metadata. Up to 20 results per page, across up to 4 pages.

## 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": [
      "query"
     ],
     "properties": {
      "page": {
       "type": "integer",
       "default": 1,
       "maximum": 4,
       "minimum": 1,
       "description": "Page number for pagination (1-4). Each page returns up to 20 publications."
      },
      "query": {
       "type": "string",
       "maxLength": 500,
       "description": "Search keyword (max 500 characters)."
      },
      "language": {
       "type": "string",
       "maxLength": 2,
       "minLength": 2,
       "description": "Two-letter language code, e.g. es, to rank publications in that language first"
      }
     }
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/api-direct-search-substack-publications-bc45aeab/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)