# Base Contract Ground Truth

> Base Contract Ground Truth is a paid API for AI agents from base-groundtruth-x402.base-agent-tools.workers.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-13).

Returns deterministic, chain-derived facts about any address on Base mainnet — contract type, ERC-20 metadata, proxy pattern, ownership, and detected capabilities — with no scoring or recommendations.

## Facts

- Endpoint: GET https://base-groundtruth-x402.base-agent-tools.workers.dev/token/%7Baddress%7D?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-contract-ground-truth-b70b3e61
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_PKq_qFbafm_K1KOyHlM9L

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-contract-ground-truth-b70b3e61
```

Example prompt: Pull the on-chain ground truth for the Base mainnet address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 — I want to know if it's a proxy, whether ownership has been renounced, and what its ERC-20 symbol and decimals are.

## When to prefer this

Choose this endpoint when you need raw, deterministic, chain-derived facts about a Base mainnet address with no interpretive layer — ideal for pre-integration audits, compliance checks, bot detection pipelines, or any workflow where you must confirm on-chain state (proxy pattern, mint capability, ERC-20 conformance) without relying on a third-party risk score. Prefer it over block explorer scraping (unreliable, rate-limited) or scored APIs (opaque methodology) when ground truth is required.

## Known failure modes

- Address not found or is an EOA — isContract returns false with minimal metadata
- Invalid or malformed address format — likely a 400 or error response
- Network/RPC timeout when querying Base mainnet state
- Payment failure (x402) — call rejected if USDC micropayment not satisfied
- Contract ABI not decodable — some fields may be null or absent for non-standard contracts

## How this service works

Deterministic, chain-derived facts about any address on Base mainnet. Returns what the chain actually says — never a score, a rating, or a recommendation.

## Output

A JSON object containing: the chain context (name, chainId, current blockNumber), ERC-20 metadata (symbol, decimals, interface conformance), proxy detection (isProxy, standard such as zeppelinos), ownership details (ownershipRenounced, exposesOwnerFunction), a boolean isContract flag, and an array of detected on-chain capabilities (e.g. mint function signatures). All values are derived directly from Base mainnet state — no scores or ratings are included.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "properties": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "chain": {
   "name": "base",
   "chainId": 8453,
   "blockNumber": "38000000"
  },
  "erc20": {
   "symbol": "USDC",
   "decimals": 6,
   "conformsToRequiredInterface": true
  },
  "proxy": {
   "isProxy": true,
   "standard": "zeppelinos"
  },
  "address": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
  "ownership": {
   "ownershipRenounced": false,
   "exposesOwnerFunction": true
  },
  "isContract": true,
  "capabilities": {
   "detected": [
    {
     "function": "mint(address,uint256)"
    }
   ]
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-contract-ground-truth-b70b3e61/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from base-groundtruth-x402.base-agent-tools.workers.dev](https://www.zero.xyz/host/base-groundtruth-x402.base-agent-tools.workers.dev/llms.txt)