# Avasis ERC-20 Allowance Checker (Ethereum) > Avasis ERC-20 Allowance Checker (Ethereum) is a paid API for AI agents from agents.avasis.ai, paid per call via x402, $0.02/call, status unknown (last checked 2026-11-02). Returns the current ERC-20 token allowance a spender has over an owner's tokens on Ethereum, with optional approval sufficiency check and ready-to-sign calldata. ## Facts - Endpoint: GET https://agents.avasis.ai/v1/eth/erc20-allowance?utm_source=zero.xyz - Price: $0.02/call - Payment: x402 - Status: unknown - Last checked: 2026-11-02 - Activations on Zero: 0 - Tags: x402 - Canonical page: https://www.zero.xyz/c/avasis-erc-20-allowance-checker-ethereum-c574f4ad - Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_q0Tl5B-97gZ_CGwR-UUmg 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 avasis-erc-20-allowance-checker-ethereum-c574f4ad ``` Example prompt: Check how much USDC allowance my wallet 0x8fae03e3e0cb922297495bc22ee2a7c997f89b8d has granted to Uniswap Permit2 (0x000000000022d473030f116ddee9f6b43ac78ba3) on Ethereum, and tell me if it's enough to cover a 250 USDC transfer — also give me the calldata to revoke if it's unlimited. ## When to prefer this Use this endpoint when you need a single, structured, pay-per-call lookup of ERC-20 allowances on Ethereum without requiring an API key or account — especially useful for agents performing pre-trade safety checks, approval audits, or generating revoke/approve calldata before signing a transaction. Prefer it over raw RPC calls when you also want enriched metadata (known spender names, USD exposure, Permit2 flags, and ready-to-sign calldata) in one response. ## Known failure modes - Invalid or malformed owner/token/spender address returns a 400 error - Token contract does not exist or is not ERC-20 compliant causes RPC call failure - Network congestion or RPC timeout may delay response - Unsupported chain identifier returns an error (only ethereum/1 on this route) - Amount field with non-numeric value causes parsing error ## How this service works ERC-20 allowance check on Ethereum (chain 1, $0.02): owner + token + spender -> allowance (raw + units, unlimited flag), balance, spendable now = min(allowance, balance), USD exposure, spender code check (EOA = drainer pattern), Permit2 note. Add amount for a needs-approval check (shortfall) + approve calldata; revoke calldata always. Phrases: erc20 allowance, token approval check, needs approval, approve calldata, revoke approval. GET or POST JSON. Not an ERC-20 -> 404, never charged. ## Output A JSON object containing the current allowance (raw and human-readable), whether it is unlimited, the owner's token balance and USD exposure, the spendable_now amount, a verdict on whether the allowance is sufficient for the requested amount, any shortfall, ready-to-sign approve and revoke calldata, recognized names for the token and spender (e.g. USDC Circle, Uniswap Permit2), and a plain-English headline summarizing the situation. ## Request schema (JSON Schema) ```json { "type": "object", "$schema": "https://json-schema.org/draft/2020-12/schema", "required": [ "input" ], "properties": { "input": { "type": "object", "required": [ "type", "method" ], "properties": { "type": { "type": "string", "const": "http" }, "method": { "enum": [ "GET" ], "type": "string" }, "queryParams": { "type": "object", "required": [ "owner", "token", "spender" ], "properties": { "chain": { "type": "string", "description": "optional; must be ethereum / 1 on this route" }, "owner": { "type": "string", "description": "the token holder whose approval you are checking (0x + 40 hex)" }, "token": { "type": "string", "description": "ERC-20 token contract on Ethereum (0x + 40 hex)" }, "amount": { "type": "string", "description": "optional amount in token units (e.g. 100.5): adds the needs-approval check (sufficient allowance / balance, shortfall) and exact approve calldata" }, "spender": { "type": "string", "description": "the contract or account that would call transferFrom (router, Permit2, bridge, ...) (0x + 40 hex)" } }, "additionalProperties": false } }, "additionalProperties": false }, "output": { "type": "object", "required": [ "type" ], "properties": { "type": { "type": "string" }, "example": { "type": "object", "required": [ "chain", "token", "owner", "spender", "allowance", "spendable_now", "calldata", "headline" ], "properties": { "usd": { "type": "object" }, "kind": { "type": "string" }, "rail": { "type": "string" }, "chain": { "type": "string" }, "check": { "type": [ "object", "null" ] }, "owner": { "type": "string" }, "token": { "type": "object" }, "spender": { "type": "object" }, "calldata": { "type": "object" }, "chain_id": { "type": "integer" }, "headline": { "type": "string" }, "allowance": { "type": "object" }, "block_number": { "type": "integer" }, "owner_balance": { "type": "object" } … (truncated) ``` ## Response schema (JSON Schema) ```json { "type": "json", "example": { "usd": { "note": "exposure = spendable_now at the current price", "price": 1, "exposure": 11285.04, "allowance": null, "price_source": "stablecoin peg (known issuer)", "owner_balance": 11285.04 }, "kind": "erc20-allowance", "rail": "evm-rails-1", "chain": "ethereum", "check": { "amount": "250", "verdict": "READY: the spender can move this amount now", "amount_raw": "250000000", "needs_approval": false, "shortfall_balance": "0", "sufficient_balance": true, "shortfall_allowance": "0", "sufficient_allowance": true, "approve_exact_calldata": null }, "owner": "0x8fae03e3e0cb922297495bc22ee2a7c997f89b8d", "reads": { "rpc": "fixture", "calls": 8, "elapsed_ms": 0 }, "token": { "known": "USDC (Circle)", "symbol": "USDC", "address": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913", "decimals": 6, "decimals_source": "decimals()" }, "spender": { "note": "Permit2 keeps its own per-spender allowances on top of this ERC-20 approval", "known": "Uniswap Permit2", "address": "0x000000000022d473030f116ddee9f6b43ac78ba3", "permit2": true, "is_contract": true }, "calldata": { "to": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913", "from": "the owner", "note": "approve(spender, amount) as 0x calldata, ready to sign from the owner; prefer an exact amount over unlimited; revoke = approve(spender, 0). Simulate first: /v1//tx-precheck", "revoke": "0x095ea7b3000000000000000000000000000000000022d473030f116ddee9f6b43ac78ba30000000000000000000000000000000000000000000000000000000000000000", "approve_exact": null, "approve_unlimited": "0x095ea7b3000000000000000000000000000000000022d473030f116ddee9f6b43ac78ba3ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff" }, "chain_id": 1, "headline": "USDC on Base: 0x8fae…9b8d allows Uniswap Permit2 UNLIMITED; balance 11,285.039971 (exposure $11,285.04); READY for 250", "allowance": { "raw": "115792089237316195423570985008687907853269984665640564039457584007913129639935", "zero": false, "amount": "115792089237316195423570985008687907853269984665640564039457584007913129.639935", "unlimited": true, "pct_of_balance": 100 }, "block_number": 53354727, "owner_balance": { "raw": "11285039971", "error": null, "amount": "11285.039971" }, "spendable_now": { "raw": "11285039971", "note": "what the spender could move right now = min(allowa … (truncated) ``` ## More - Live health (JSON, refreshed every minute): https://www.zero.xyz/c/avasis-erc-20-allowance-checker-ethereum-c574f4ad/health.json - [Zero catalog index](https://www.zero.xyz/llms.txt) - [Other services from agents.avasis.ai](https://www.zero.xyz/host/agents.avasis.ai/llms.txt)