# BaseBrief x402 — Base Address State (Gas, Balances, Tokens, Allowances)

> BaseBrief x402 — Base Address State (Gas, Balances, Tokens, Allowances) is a paid API for AI agents from basebrief-x402.savannah-5966.chatgpt.site, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-15).

Returns point-in-time on-chain state for a Base mainnet address: ETH/token balances, gas data, token metadata, and ERC-20 allowances.

## Facts

- Endpoint: GET https://basebrief-x402.savannah-5966.chatgpt.site/api/v1/base/address
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/basebrief-x402-base-address-state-gas-balances-tokens-allowances-0bb7a93d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_BNjgfxBjpEOsybaIZHMKl

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 basebrief-x402-base-address-state-gas-balances-tokens-allowances-0bb7a93d
```

Example prompt: What's the current ETH balance, token holdings, and any ERC-20 allowances for Base address 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045 right now on Base mainnet?

## When to prefer this

Choose this endpoint when you need live, point-in-time on-chain state for a specific Base mainnet address — especially gas prices, token balances, ERC-20 allowances, and token metadata — without running your own Base RPC node. Ideal for AI agents that need to verify wallet state before executing transactions or reporting portfolio data on Base (chain ID 8453). Prefer this over generic Ethereum endpoints when the target chain is specifically Base mainnet.

## Known failure modes

- Invalid or malformed address (not matching ^0x[0-9a-fA-F]{40}$) returns a validation error
- Address not found or zero-balance address may return empty token/balance arrays
- Payment not included or insufficient (x402 payment required) returns 402 Payment Required
- Base RPC node temporarily unavailable may cause timeout or 503
- Rate limiting if too many requests in a short window

## How this service works

Gas, balances, token metadata and allowances for $0.004 per result.

## Output

A JSON object with point-in-time on-chain evidence: chain name, chain ID (8453), current block number, ETH balance, ERC-20 token balances with metadata (symbol, decimals, name), and spender allowances for the queried address. Also includes a limitations array noting the point-in-time nature of the data.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "address"
     ],
     "properties": {
      "address": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "description": "Base mainnet address address."
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "required": [
      "evidence",
      "limitations"
     ],
     "properties": {
      "evidence": {
       "type": "object",
       "additionalProperties": true
      },
      "limitations": {
       "type": "array",
       "items": {
        "type": "string"
       }
      }
     },
     "additionalProperties": true
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "evidence": {
   "chain": "Base mainnet",
   "chainId": 8453,
   "blockNumber": "35123456",
   "pointInTime": true
  },
  "limitations": [
   "Point-in-time direct Base JSON-RPC evidence."
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/basebrief-x402-base-address-state-gas-balances-tokens-allowances-0bb7a93d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from basebrief-x402.savannah-5966.chatgpt.site](https://www.zero.xyz/host/basebrief-x402.savannah-5966.chatgpt.site/llms.txt)