# Base Onchain Data – Address Type & Contract Metadata

> Base Onchain Data – Address Type & Contract Metadata is a paid API for AI agents from ca-tax-api-mainnet.lxtap.workers.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-23).

Identifies whether a Base address is a wallet (EOA) or contract, and returns token standard, name, symbol, proxy details, bytecode size, nonce, and ETH balance.

## Facts

- Endpoint: GET https://ca-tax-api-mainnet.lxtap.workers.dev/base/contract?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-23
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-onchain-data-address-type-contract-metadata-4a35ed3b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_fuy8SkT2E6Fk9_hs3Vhdg

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-onchain-data-address-type-contract-metadata-4a35ed3b
```

Example prompt: Can you look up what's at Base address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 — is it a wallet or a contract, what token standard does it use, and what's its name and symbol?

## When to prefer this

Use this endpoint when you need to classify a Base network address and retrieve rich contract metadata in a single call — especially when you need token standard, proxy details, and balance together. Prefer this over general blockchain explorers when building automated agents that need structured, machine-readable onchain data for Base specifically. Choose this over the Ethereum or OP Mainnet equivalents when the target address is on the Base L2 network.

## Known failure modes

- Invalid address format (not a valid 0x-prefixed 40-hex-char address) returns a validation error
- Address not found or network error returns an API error
- Contract does not implement a recognized token standard — token fields returned as null or empty
- RPC/node timeout causes delayed or failed response
- Newly deployed contract may have incomplete or missing metadata

## How this service works

Pay-per-call data for AI agents, paid in USDC on Base with x402: token risk checks (rug check) on Base, Ethereum, Arbitrum, Optimism, Polygon and Solana, onchain reads (balances, transactions, gas, contracts, NFTs, whale trades, new pools, ENS and Basenames), ECB exchange rates, and Canadian sales tax and business days.

## Output

Returns whether the address is an EOA or contract, the token standard it implements (ERC-20, ERC-721, ERC-1155, or none), the token name and symbol, proxy implementation and admin addresses if applicable, bytecode size in bytes, the address nonce, and current ETH balance.

## Request schema (JSON Schema)

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

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "kind": "ERC-20 token",
  "name": "USD Coin",
  "chain": "base",
  "proxy": {
   "admin": "0x4fc7850364958d97B4d3f5A08f79db2493f8cA44",
   "upgradeable": true,
   "implementation": "0x2Ce6311ddAE708829bc0784C967b7d77D19FD779"
  },
  "symbol": "USDC",
  "address": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
  "decimals": 6,
  "standards": {
   "erc20": true,
   "erc165": false,
   "erc721": false,
   "erc1155": false
  },
  "isContract": true,
  "totalSupply": "4291989037.45169",
  "bytecodeBytes": 1852,
  "nativeBalance": "0.009800646158085843"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-onchain-data-address-type-contract-metadata-4a35ed3b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from ca-tax-api-mainnet.lxtap.workers.dev](https://www.zero.xyz/host/ca-tax-api-mainnet.lxtap.workers.dev/llms.txt)