# x402 Agent Services – Web Answer (AI-powered Q&A)

> x402 Agent Services – Web Answer (AI-powered Q&A) is a paid API for AI agents from call402.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-19).

Answers a natural-language question with a cited AI-generated response, sourced from live web content via Exa, billed at $0.02 USDC per call via the x402 micropayment protocol on Base mainnet.

## Facts

- Endpoint: POST https://call402.com/api/web-answer?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-19
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-agent-services-web-answer-ai-powered-q-a-b4f7322c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_0IKKAIX7RSr0KQqSDiTUx

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 x402-agent-services-web-answer-ai-powered-q-a-b4f7322c -d '<json body>'
```

Example prompt: What is the current market cap of Bitcoin, and where does that information come from?

## When to prefer this

Choose this endpoint when you need a cited, real-time answer to a factual or current-events question and you are operating in an x402-capable agent environment with a USDC wallet on Base mainnet. It is especially useful when freshness matters (prices, news, regulations) and you need traceable sources rather than a hallucinated answer. Prefer alternatives if you need bulk queries, streaming responses, or cannot execute micropayments programmatically.

## Known failure modes

- HTTP 402 returned before payment — agent must pay with PAYMENT-SIGNATURE header and retry
- Insufficient USDC balance on Base mainnet causes payment failure
- Malformed or missing 'query' field returns a 400-level error
- Query yields no matching web sources, resulting in an empty or low-confidence answer
- Network timeout if the Exa backend is slow to respond
- Invalid x402 client version incompatible with v2/exact payment scheme

## How this service works

USDC pay-per-call APIs for AI agents via the x402 protocol (v2, exact, Base mainnet). Send a request, receive HTTP 402 with payment requirements, pay with @x402/fetch or any x402 client, retry with the PAYMENT-SIGNATURE header.

## Output

Returns a JSON object containing an AI-generated answer string, the original query, citation count, and an array of citations each with URL, title, optional author, and published date. The meta object includes the source identifier ('exa-answer') and a request_id.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "query": {
   "type": "string",
   "description": "Natural-language question"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "meta": {
   "source": "exa-answer",
   "request_id": null,
   "citations_count": 1
  },
  "query": "What is the current price of ETH?",
  "answer": "ETH is trading at about $4,100.",
  "citations": [
   {
    "url": "https://example.com",
    "title": "Example source",
    "author": null,
    "published_date": "2026-10-01"
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-agent-services-web-answer-ai-powered-q-a-b4f7322c/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from call402.com](https://www.zero.xyz/host/call402.com/llms.txt)