# BaseBrief x402 – Base Chain Token State Lookup

> BaseBrief x402 – Base Chain Token State Lookup 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 gas prices, token balances, token metadata, and allowances for a given Base mainnet address, charged at $0.004 per call via x402.

## Facts

- Endpoint: GET https://basebrief-x402.savannah-5966.chatgpt.site/api/v1/base/token
- 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-chain-token-state-lookup-60773250
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_H1MPeFT7cBdjo2P-c0e8i

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-chain-token-state-lookup-60773250
```

Example prompt: Can you pull the current token balances, gas price, and any ERC-20 allowances for the Base mainnet address 0xAbCd1234...5678 right now?

## When to prefer this

Choose this endpoint when you need real-time, point-in-time on-chain state for a Base mainnet address — specifically gas prices, token balances, ERC-20 metadata, or allowances — in a single cheap paid call ($0.004). Prefer it over general Ethereum RPC endpoints when you specifically need Base L2 data and want a structured, agent-friendly JSON response without managing your own RPC infrastructure. It is especially suitable for AI agents that need to check wallet state before executing DeFi operations or building portfolio dashboards.

## Known failure modes

- Invalid address format (not matching ^0x[0-9a-fA-F]{40}$) returns a validation error
- Missing required `address` query parameter returns a 400 bad request
- Payment not provided or insufficient USDC causes x402 payment-required response
- Base JSON-RPC node unavailability may cause timeouts or 5xx errors
- Querying a non-existent or zero-balance address returns valid empty/zero data rather than an error

## How this service works

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

## Output

A JSON object containing point-in-time on-chain evidence for the queried Base mainnet address, including: current gas price, native and ERC-20 token balances, token metadata (symbol, decimals, name), allowances for specified spenders, the current block number, chain ID (8453), and a limitations array noting the data is a point-in-time snapshot from Base JSON-RPC.

## 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-chain-token-state-lookup-60773250/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)