# Base Token Check

> Base Token Check is a paid API for AI agents from api.facts402.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-11-01).

Returns on-chain facts for a Base mainnet ERC-20 token contract: name, symbol, decimals, totalSupply, proxy status, owner, and presence of mint/pause/blacklist selectors in bytecode.

## Facts

- Endpoint: POST https://api.facts402.com/check?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-11-01
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-token-check-daab809c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__HbGEmcq8TPdxZsrwWAny

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-token-check-daab809c -d '<json body>'
```

Example prompt: Can you pull the on-chain facts for the Base mainnet token at 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 — I want to know its name, symbol, decimals, total supply, whether it's an EIP-1967 proxy, who the owner is, and if mint, pause, or blacklist selectors show up in the bytecode?

## When to prefer this

Use this endpoint when you need authoritative, raw on-chain facts about a Base mainnet token contract — especially for due diligence, risk flagging, or pre-trade checks — and you specifically want bytecode-level inspection for mint/pause/blacklist selectors and EIP-1967 proxy detection. Prefer this over generic block explorers when you need programmatic, structured output for agent workflows. Not suitable for tokens on other chains (Ethereum mainnet, Polygon, etc.) or for price/liquidity data.

## Known failure modes

- Invalid or malformed contract address (not matching ^0x[0-9a-fA-F]{40}$) returns a validation error
- Address is not a deployed contract on Base mainnet (chain ID 8453) — returns not-a-contract or empty response
- Contract exists but does not expose standard ERC-20 methods — partial results returned
- RPC connectivity issues to Base mainnet may cause timeouts
- Payment failure via x402 protocol results in 402 response before any data is returned

## How this service works

Use when an agent needs raw facts about a Base ERC-20 contract, not a verdict: name, symbol, decimals, totalSupply, EIP-1967 proxy status, owner() and mint/pause/blacklist selectors in bytecode. Facts only, no ratings. $0.01 USDC on Base; charged only on 2xx, never for invalid input.

## Output

Returns a structured fact sheet for the given Base mainnet token contract including: human-readable name and symbol, decimals, totalSupply (raw), whether the contract is an EIP-1967 proxy and its implementation address, the owner() address if exposed, and boolean flags indicating whether mint, pause, and blacklist function selectors are present in the contract bytecode. No ratings or opinions — raw on-chain facts only.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "token": {
   "type": "string",
   "pattern": "^0x[0-9a-fA-F]{40}$",
   "description": "Base mainnet (chain id 8453) token contract address"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-token-check-daab809c/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.facts402.com](https://www.zero.xyz/host/api.facts402.com/llms.txt)