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ERC-721 Balance Checker (Multi-Chain)
x402
ERC-721 Balance Checker (Multi-Chain) is a paid API for AI agents from biosfera.46-62-215-147.sslip.io, paid per call via x402, $0.001/call, status down (last checked 2026-10-02).
Returns the number of ERC-721 NFTs a wallet address holds in a given collection on Base, Ethereum, Arbitrum, Optimism, or Polygon.
Price / call$0.001
Success—
StatusDown
How this service works
Use when you need how many tokens of an ERC-721 collection an address holds on Base, Ethereum, Arbitrum, Optimism or Polygon, via balanceOf, with the collection name.
Output
Returns the NFT token count (integer balance) for the specified wallet address in the given ERC-721 contract on the requested chain, along with the collection name.
Example use cases
NFT holder eligibility check
“Can you check how many tokens the wallet 0xAb5801a7D398351b8bE11C439e05C5B3259aeC9B holds in the NFT collection at 0x60E4d786628Fea6478F785A6d7e704777c86a7c6 on Ethereum? I need to know if they qualify as a holder.”
Portfolio NFT count on Base
“How many NFTs does the address 0x1234567890abcdef1234567890abcdef12345678 hold in the collection at contract 0xabcdefabcdefabcdefabcdefabcdefabcdefabcd on Base?”
Cross-chain NFT balance audit
“Tell me how many tokens the wallet 0xdead000000000000000042069420694206942069 owns in the ERC-721 collection deployed at 0xBd3531dA5CF5857e7CfAA92426877b022e612cf8 on Polygon.”
Technical details
Endpoint
GEThttps://biosfera.46-62-215-147.sslip.io/o/erc721-balance?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to know the raw NFT count a wallet holds in a specific ERC-721 collection across the five supported chains (Base, Ethereum, Arbitrum, Optimism, Polygon). Prefer this over general NFT portfolio APIs when you already know the contract address and just need the balanceOf result without extra metadata overhead.
Side effects
- Invalid wallet or contract address format (must be 0x + 40 hex chars)
- Unsupported chain value outside of base/ethereum/arbitrum/optimism/polygon
- Contract address is not a valid ERC-721 contract on the specified chain
- Network congestion or RPC node unavailability causing timeout
- Payment failure due to insufficient USDC balance for x402 micropayment
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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