# Base NFT Metadata URI Lookup

> Base NFT Metadata URI Lookup is a paid API for AI agents from x402.agentindex.world, paid per call via x402, $0.008/call, status unknown (last checked 2026-10-11).

Returns the tokenURI (IPFS, HTTP, or data URI) for a given ERC721 token on Base mainnet, providing the on-chain metadata pointer without fetching the document itself.

## Facts

- Endpoint: GET https://x402.agentindex.world/base/nft-metadata?utm_source=zero.xyz
- Price: $0.008/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-nft-metadata-uri-lookup-c9f26054
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_nTC7B2K3_qX64-RuIzJGy

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-nft-metadata-uri-lookup-c9f26054
```

Example prompt: What's the tokenURI stored on-chain for token ID 1337 of the NFT contract 0xd4307e0acd12cf46fd6cf93bc264f5d5d1598792 on Base mainnet?

## When to prefer this

Choose this endpoint when you need the raw on-chain tokenURI pointer for an ERC721 NFT on Base mainnet — for example, to verify where metadata is hosted (IPFS vs centralized), to build indexers, or to check if a URI is still valid before fetching. Prefer this over off-chain NFT APIs when you need the ground-truth on-chain value rather than a cached or enriched version. If you need the actual metadata document contents (name, image, traits), you'll need to follow up by fetching the returned URI separately.

## Known failure modes

- Contract address does not exist on Base mainnet — call reverts or returns empty
- Token ID does not exist or has not been minted — tokenURI call reverts
- Contract is not ERC721 or does not implement tokenURI — returns error or empty string
- Malformed contract address input — validation error
- Network congestion or RPC timeout — slow or failed response
- Token has been burned — tokenURI may revert

## How this service works

NFT metadata URI for an ERC721 token on Base mainnet via tokenURI - the on-chain pointer (IPFS, HTTP, or data URI), not a fetch of the document itself.

## Output

Returns the raw tokenURI string as stored on-chain for the specified ERC721 token — this may be an IPFS URI (ipfs://...), an HTTP/HTTPS URL, or a base64-encoded data URI. The endpoint does NOT fetch or decode the document at that URI; it only returns the pointer itself.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "token": {
   "type": "string",
   "title": "Token"
  },
  "token_id": {
   "type": "integer",
   "title": "Token Id",
   "minimum": 0
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-nft-metadata-uri-lookup-c9f26054/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402.agentindex.world](https://www.zero.xyz/host/x402.agentindex.world/llms.txt)