# Open Library Subject Book Search

> Open Library Subject Book Search is a paid API for AI agents from proxy.suverse.io, paid per call via x402, $0.05/call, status unknown (last checked 2026-09-14).

Returns books (works) from Open Library tagged with a given subject, along with work counts and metadata, without requiring an API key.

## Facts

- Endpoint: POST https://proxy.suverse.io/v1/data/suverse-openlibrary-subject
- Price: $0.05/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/open-library-subject-book-search-b8385182
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_nDvs4rCi5fttFQ8530B-U

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 open-library-subject-book-search-b8385182 -d '<json body>'
```

Example prompt: Can you look up books about ancient Roman history on Open Library and show me what works come up along with how many there are?

## When to prefer this

Choose this endpoint when you need keyless, no-authentication book discovery by topic from Open Library's large public catalog. Ideal for agents that need bibliographic data without managing API credentials, and when subject-level browsing (rather than title or author search) is the primary intent.

## Known failure modes

- Subject not found or no works tagged — returns empty results or zero count
- Misspelled or ambiguous subject term yields irrelevant or no results
- Open Library upstream outage causes timeout or error response
- POST body missing required fields returns validation error
- Rate limiting or payment failure via x402 protocol blocks the call

## How this service works

Books for a subject from Open Library, no key. Returns works tagged with the subject plus counts. For AI agents discovering books by topic.

## Output

Returns a list of works from Open Library tagged with the requested subject, including book titles, author information, and total work counts for that subject.

## 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",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "properties": {}
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST",
      "PUT",
      "PATCH"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/open-library-subject-book-search-b8385182/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from proxy.suverse.io](https://www.zero.xyz/host/proxy.suverse.io/llms.txt)