# Hearth AI Chat (x402 Pay-Per-Call)

> Hearth AI Chat (x402 Pay-Per-Call) is a paid API for AI agents from 138-197-15-135.sslip.io, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-31).

Runs a single-turn LLM prompt-completion via a pay-per-call API, billed at $0.002 USDC per request using the x402 micropayment protocol on Base.

## Facts

- Endpoint: GET https://138-197-15-135.sslip.io/v1/ai/chat?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hearth-ai-chat-x402-pay-per-call-732c204e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_FXdZ9lp1PIgTkS42DwRWb

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 hearth-ai-chat-x402-pay-per-call-732c204e
```

Example prompt: Ask the AI chat endpoint to summarize the following in 2 sentences using up to 300 tokens: 'Blockchain technology enables decentralized, trustless record-keeping across distributed networks, removing the need for central intermediaries.'

## When to prefer this

Choose this endpoint when you need a low-cost, pay-per-call LLM inference with no subscription or API key required, settled instantly in USDC on Base via x402. It's ideal for agents that need occasional or bursty LLM completions, want to avoid monthly billing, or are already operating in the x402 micropayment ecosystem. Not suitable for long-form generation (>600 tokens), streaming responses, or multi-turn conversation state.

## Known failure modes

- Payment not received or x402 handshake fails — returns 402 Payment Required
- Prompt exceeds 2000 character limit — request rejected with validation error
- max_tokens out of range (below 16 or above 600) — server returns error
- Model unavailable or upstream OpenAI outage — text field returns null
- Rate limiting if too many calls in short succession

## How this service works

One-shot LLM completion for agents: send a prompt (and optional system message), get the answer text. Flat $0.002 per call, no account or API key; cheaper than typical x402 chat proxies. Up to ~2,000 chars of prompt and 600 output tokens. GET or POST JSON {prompt, system}.

## Output

Returns a JSON object containing the generated text string, the model identifier (e.g. 'gpt-5-nano'), and a usage object with promptTokens and completionTokens counts. The text field may be null on failure.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "queryParams"
   ],
   "properties": {
    "queryParams": {
     "type": "object",
     "required": [
      "prompt"
     ],
     "properties": {
      "prompt": {
       "type": "string",
       "description": "User prompt (max 2000 chars)"
      },
      "system": {
       "type": "string",
       "description": "Optional system message (max 1000 chars)"
      },
      "max_tokens": {
       "type": "string",
       "description": "Max output tokens, 16-600 (default 400)"
      }
     }
    }
   }
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "json"
    },
    "example": {
     "type": "object",
     "required": [],
     "properties": {
      "text": {
       "type": [
        "string",
        "null"
       ]
      },
      "model": {
       "type": [
        "string",
        "null"
       ]
      },
      "usage": {
       "type": [
        "object",
        "null"
       ]
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "text": "bullish",
  "model": "gpt-5-nano",
  "usage": {
   "promptTokens": 30,
   "completionTokens": 2
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hearth-ai-chat-x402-pay-per-call-732c204e/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from 138-197-15-135.sslip.io](https://www.zero.xyz/host/138-197-15-135.sslip.io/llms.txt)