# Answer Engine with Citations

> Answer Engine with Citations is a paid API for AI agents from agentsvc.io, paid per call via x402, $0.008/call, status unknown (last checked 2026-10-11).

Returns an AI-generated answer to a natural language question along with cited source URLs from web, news, or Wikipedia

## Facts

- Endpoint: POST https://agentsvc.io/api/v1/proxy/answer-with-sources?utm_source=zero.xyz
- Price: $0.008/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/answer-engine-with-citations-586dfa90
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_oVGjuhDi6jLaTyaN8x7Vw

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 answer-engine-with-citations-586dfa90 -d '<json body>'
```

Example prompt: Can you look up what a Legal Entity Identifier is and give me a sourced answer with links I can verify — search the web for it?

## When to prefer this

Choose this endpoint when you need a factual answer grounded in verifiable sources rather than a raw search result list or an unattributed AI response. It's ideal when you need citations alongside the answer for transparency, fact-checking, or user trust. Prefer it over plain web-scraping when you want synthesized prose rather than raw HTML, and over a bare LLM call when you need source attribution. Best for factual, research-oriented, or news-backed questions up to 400 characters.

## Known failure modes

- Question exceeds 400-character limit — returns error
- No relevant sources found for highly niche questions — answer may be unsourced or low-confidence
- Network or upstream search failure — returns error or empty sources
- Language not recognized — may default to English output
- Ambiguous source selection when source=auto — may not match user intent

## How this service works

86 APIs for AI agents: web scraping and crawling to Markdown, AI summaries, data extraction and cited answers, screenshots and PDF, PDF, OCR and document conversion, news, paper and developer search and more, paid per call with USDC on Base, Solana, Polygon or Arbitrum via x402. No account, no API key, free sample on every service.

## Output

A JSON object containing a natural-language answer generated by Claude, a list of numbered source citations with URLs and titles, the original question, which sources were searched (web/news), a timestamp, and the model name used. Sources are drawn from Wikipedia, GDELT news index, and Hacker News.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "source": {
   "enum": [
    "auto",
    "news",
    "web"
   ],
   "type": "string",
   "default": "auto"
  },
  "language": {
   "type": "string",
   "description": "Answer language, e.g. German; default English"
  },
  "question": {
   "type": "string",
   "description": "The question, max 400 chars"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "data": {
   "note": "Sources come from Wikipedia and our news index (GDELT, Hacker News), not from...",
   "model": "claude-haiku-5-5",
   "answer": "A Legal Entity Identifier (LEI) is a unique 20-character alphanumeric code th...",
   "sources": [
    {
     "n": 1,
     "url": "https://en.wikipedia.org/wiki/Legal_Entity_Identifier",
     "title": "Legal Entity Identifier - Wikipedia"
    }
   ],
   "question": "What is a Legal Entity Identifier used for?",
   "searched": [
    "web"
   ],
   "answered_at": "2026-10-10T09:58:26.892Z"
  },
  "success": true
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/answer-engine-with-citations-586dfa90/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agentsvc.io](https://www.zero.xyz/host/agentsvc.io/llms.txt)