# Linkrra Pearl Pool — USDC Top-Up via x402

> Linkrra Pearl Pool — USDC Top-Up via x402 is a paid API for AI agents from pool.linkrra.com, paid per call via x402, $1/call, status unknown (last checked 2026-10-11).

Tops up a Linkrra Pearl Pool account balance by initiating a USDC payment on Base via the x402 payment protocol, returning the updated credit balance.

## Facts

- Endpoint: POST https://pool.linkrra.com/api/billing/x402/topup?utm_source=zero.xyz
- Price: $1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/linkrra-pearl-pool-usdc-top-up-via-x402-470d2151
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_nVY_IQhIkQr89sIySPsVt

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 linkrra-pearl-pool-usdc-top-up-via-x402-470d2151 -d '<json body>'
```

Example prompt: I want to top up my Linkrra Pearl Pool account with $10 USDC on Base so I can keep running inference requests — go ahead and submit the payment via x402.

## When to prefer this

Choose this endpoint when you need to add USDC credits to a Linkrra Pearl Pool account to fund subsequent OpenAI-compatible inference API calls paid per-request via x402. This is the correct endpoint for account top-ups, not for making inference calls directly. Prefer this over generic crypto transfer APIs because it integrates directly with Linkrra's credit system and returns a verified updated balance.

## Known failure modes

- Payment rejected if x402 challenge response is invalid or malformed
- Insufficient USDC balance in the paying wallet causes transaction failure
- Wrong network (not Base/eip155:8453) results in payment failure
- Malformed request body missing required 'input' or 'output' fields returns 4xx error
- x402 scheme mismatch if not using 'exact' scheme returns 402 challenge again
- Network congestion on Base may delay on-chain confirmation

## How this service works

OpenAI-compatible inference paid per request in USDC on Base (eip155:8453, scheme exact). GET /v1/models for the model catalogue and per-model USD prices. Every paid route answers unauthenticated requests with an x402 v2 402 challenge (PAYMENT-REQUIRED header + JSON body). Contact: weare@linkrra.com

## Output

Returns a JSON object with a boolean 'ok' field confirming success, plus 'balance' and 'credits' fields showing the updated account balance in micro-USDC units (e.g. {ok: true, balance: 4399472, credits: 4399472}).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "input",
  "output"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object"
    },
    "type": {
     "type": "string"
    },
    "method": {
     "type": "string"
    },
    "bodyType": {
     "type": "string"
    }
   }
  },
  "output": {
   "type": "object",
   "required": [
    "type",
    "example"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "balance": 4399472,
  "credits": 4399472
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/linkrra-pearl-pool-usdc-top-up-via-x402-470d2151/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from pool.linkrra.com](https://www.zero.xyz/host/pool.linkrra.com/llms.txt)