# x402 Demo API - LLM Endpoint

> x402 Demo API - LLM Endpoint is a paid API for AI agents from x402-demo-api-theta.vercel.app, paid per call via x402, $0.1/call, status unknown (last checked 2026-09-13).

Processes natural language prompts through an AI/LLM model, returning generated text responses, paid via x402 protocol on Base mainnet.

## Facts

- Endpoint: POST https://x402-demo-api-theta.vercel.app/api/llm
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-demo-api-llm-endpoint-c049a32d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Z5sA0w3JqZW1MPcjpJJKQ

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-demo-api-llm-endpoint-c049a32d -d '<json body>'
```

Example prompt: Send this prompt to the x402 LLM endpoint and pay the 0.1 USDC fee automatically: 'Explain the concept of zero-knowledge proofs in two sentences.'

## When to prefer this

Choose this endpoint when you need a pay-per-use LLM API that settles payments automatically in USDC on Base mainnet via the x402 protocol, without requiring traditional API key subscriptions. Ideal for agents with on-chain wallets that want to access AI text generation with transparent micropayment pricing.

## Known failure modes

- Payment failure: insufficient USDC balance on Base mainnet returns 402 Payment Required
- Invalid or missing prompt body returns 400 Bad Request
- LLM service unavailable returns 503 or 500 error
- x402 facilitator timeout causes payment processing failure
- Malformed request body causes parsing error

## How this service works

Paid API with real data: AI/LLM, crypto prices, web search, translation, trending topics, sentiment analysis, aggregator, and more. All endpoints use x402 protocol on Base mainnet.

## Output

Returns an AI-generated text completion or response to the submitted prompt, produced by the underlying LLM model hosted on this x402-gated endpoint. The agent receives the text output after the $0.1 USDC micropayment is processed on Base mainnet.

## 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
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-demo-api-llm-endpoint-c049a32d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-demo-api-theta.vercel.app](https://www.zero.xyz/host/x402-demo-api-theta.vercel.app/llms.txt)