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ERC-20 Allowance Checker with Balance and Sufficiency Verdict
x402
ERC-20 Allowance Checker with Balance and Sufficiency Verdict is a paid API for AI agents from api.x-402.online, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-03).
Returns the ERC-20 allowance granted by an owner to a spender (USDC by default), along with the owner's token balance and a sufficiency verdict if a target amount is provided.
Price / call$0.005
Success—
StatusUnknown
How this service works
Get an ERC-20 allowance with the owner's balance and a sufficiency verdict for the amount you plan to pull. ERC-20 allowance of a spender on an owner (USDC by default), with the owner's balance and, if you pass ?amount=, a verdict: i…
Output
Returns the current ERC-20 allowance (in token units and human-readable), the owner's token balance, the token metadata (symbol, decimals), and — if an amount was supplied — a boolean sufficiency verdict indicating whether the allowance covers the requested amount.
Example use cases
Pre-flight DeFi transaction check
“Before I approve this swap, check if the DEX contract 0xRouter...999 already has USDC allowance from my wallet 0xMyWallet...111 on Base, and whether the existing allowance covers 500 USDC.”
Agent payment authorization guard
“My agent is about to pull 100 USDC from 0xUser...222 using spender 0xAgent...333 — can you verify the allowance and balance are both sufficient before it proceeds?”
Allowance audit for a wallet
“Look up the USDC allowance that 0xProtocol...444 has over 0xHolder...555, and show me the owner's current USDC balance so I can decide whether to revoke or top up the approval.”
Technical details
Endpoint
GEThttps://api.x-402.online/v1/chain/allowance?utm_source=zero.xyzWhen to prefer
Use this endpoint when an AI agent or workflow needs to verify on-chain ERC-20 approval status before attempting a transferFrom or similar pull-payment operation — especially for USDC on Base. It combines three checks (allowance, balance, sufficiency) in a single call, avoiding multiple RPC round-trips. Prefer it over raw RPC calls when you need a human-readable verdict without writing blockchain query code.
Side effects
- Invalid or malformed owner/spender address returns a 400 error
- Unsupported chain ID or token contract returns an error or empty result
- RPC node unavailability causes a 503 or timeout
- Missing required query parameters (owner, spender) returns a 422 validation error
- Amount parameter provided in wrong format may be ignored or cause parsing error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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