# Base Stablecoin Balance Checker

> Base Stablecoin Balance Checker is a paid API for AI agents from base-agent-preflight.bytoken2023.workers.dev, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-13).

Fetches and risk-assesses stablecoin balances held by a given Base (EVM) wallet or contract address, returning balances, risk score, and safety flags.

## Facts

- Endpoint: GET https://base-agent-preflight.bytoken2023.workers.dev/v1/x402/base/stablecoin-balance
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-stablecoin-balance-checker-62f79c4d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ROo8Rhq8bDIGRgv63zOPj

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 base-stablecoin-balance-checker-62f79c4d
```

Example prompt: Before I send USDC to 0x4a2b38b9cDb1c8f9b3e5e6A5c3D4f1e2b7a8c9d0 on Base, can you check what stablecoins that address holds and whether it has any risk flags?

## When to prefer this

Use this endpoint when you need to preflight-check a Base (EIP-155:8453) wallet or contract for stablecoin holdings and associated risk before executing a transaction, payment, or integration. Prefer it over generic blockchain explorers when you want a machine-readable risk score and structured safety flags rather than raw on-chain data.

## Known failure modes

- Invalid address format (not a valid 0x EVM address) returns a validation error
- Address has no stablecoin activity on Base — returns empty balances with low risk score
- Rate limiting or payment failure (x402) if USDC payment not attached
- RPC node unavailability may cause transient 5xx errors
- Contract addresses with proxy patterns may return incomplete balance data

## How this service works

Machine-payable service intelligence for discovering, verifying, and monitoring identity, risk, authorization, execution-preflight, and evidence APIs before autonomous agents spend.

## Output

Returns a JSON object with the network identifier (eip155:8453), product label, and an assessment block containing a risk_level (e.g. 'low'), a numeric risk_score, and an array of risk flags — along with any relevant activity, identity, and provenance metadata for the queried address.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "address"
     ],
     "properties": {
      "address": {
       "type": "string",
       "pattern": "^0x[a-fA-F0-9]{40}$",
       "description": "Base wallet or contract whose stablecoin balances should be read."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "network": {
       "type": "string"
      },
      "product": {
       "type": "string"
      },
      "activity": {
       "type": "object"
      },
      "identity": {
       "type": "object"
      },
      "assessment": {
       "type": "object"
      },
      "provenance": {
       "type": "object"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "network": "eip155:8453",
  "product": "base-stablecoin-balance",
  "assessment": {
   "flags": [],
   "risk_level": "low",
   "risk_score": 0
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-stablecoin-balance-checker-62f79c4d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from base-agent-preflight.bytoken2023.workers.dev](https://www.zero.xyz/host/base-agent-preflight.bytoken2023.workers.dev/llms.txt)