# Which API Should I Call — x402 Market API Finder

> Which API Should I Call — x402 Market API Finder is a paid API for AI agents from agentsvc.io, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-21).

Search ~45,000 x402-listed API endpoints by plain-language task description to find the best matching paid APIs, with pricing, provider, network, and reachability data.

## Facts

- Endpoint: POST https://agentsvc.io/api/v1/proxy/service-finder?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-21
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/which-api-should-i-call-x402-market-api-finder-471d3a75
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_0Rad89SQusJc3ZkT-IRPg

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 which-api-should-i-call-x402-market-api-finder-471d3a75 -d '<json body>'
```

Example prompt: Search the x402 API market for endpoints that can transcribe audio to text — show me up to 5 results that accept payment on Base network and cost no more than $0.02 each, only reachable ones.

## When to prefer this

Use this endpoint when an AI agent needs to dynamically discover which x402-compatible paid API to call for a given task at runtime, rather than hardcoding a specific endpoint. It is the right choice when the agent does not know in advance which provider or URL to use, when the user's task may map to multiple competing APIs, or when you want to filter by blockchain payment network or price cap before committing to a call. Prefer this over manual API directories when you need reachability confirmation and pricing in a single lookup across ~45,000 listings.

## Known failure modes

- Task description too vague — returns low-relevance matches or empty results
- No endpoints match the requested network/price combination — returns empty result set
- All matching endpoints were unreachable and include_unreachable is false — empty results
- Task string under 3 characters or over 500 — rejected with validation error
- limit exceeds 20 — request rejected
- Network value not in enum — validation error returned

## How this service works

Find the right paid API for a task across the whole x402 market, not only agentsvc.io: describe what your agent needs in plain words ("convert a web page to markdown", "token price on Solana", "transcribe audio") and get the best matching x402 endpoints from about 45,000 listed ones, each with provider, URL, method, price in USD, payment networks, an input hint, and whether it answered our own check with a valid 402 (reachable, checked_at, response time).

## Output

A JSON array of up to 20 matching API endpoints, each containing the provider name, endpoint URL, HTTP method, price per call in USD, accepted payment networks, a plain-language input hint describing what to send, and reachability metadata (whether the endpoint returned a valid 402, when it was last checked, and response time in ms).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "task": {
   "type": "string",
   "maxLength": 500,
   "minLength": 3,
   "description": "What your agent needs, in plain words"
  },
  "limit": {
   "type": "integer",
   "default": 8,
   "maximum": 20,
   "minimum": 1
  },
  "network": {
   "enum": [
    "base",
    "solana",
    "polygon",
    "arbitrum",
    "ethereum",
    "optimism",
    "avalanche",
    "bsc"
   ],
   "type": "string",
   "description": "Only endpoints that accept payment on this network"
  },
  "max_price_usd": {
   "type": "number",
   "description": "Only endpoints at or below this price per call"
  },
  "include_unreachable": {
   "type": "boolean",
   "default": false,
   "description": "Also return endpoints that failed our last check"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "data": {},
  "success": true
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/which-api-should-i-call-x402-market-api-finder-471d3a75/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)