# 0x Swap Allowance Holder Firm Quote

> 0x Swap Allowance Holder Firm Quote is a paid API for AI agents from agent.api.0x.org, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-16).

Returns a firm (executable) swap quote using the Allowance Holder contract to manage token allowances on the 0x protocol

## Facts

- Endpoint: GET https://agent.api.0x.org/v1/x402/swap-allowance-holder-quote/%2e%2e%2fswap%2fpermit2%2fquote?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/0x-swap-allowance-holder-firm-quote-33a2072a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_KpC0g58Q9yzJOZMGjn3mA

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 0x-swap-allowance-holder-firm-quote-33a2072a
```

Example prompt: Get me a firm quote from 0x to swap 1 ETH for USDC on Ethereum mainnet using the Allowance Holder — I need the exact amount I'll receive and the transaction data to execute it.

## When to prefer this

Choose this endpoint when you need a firm, executable swap quote (not just an indicative price) and want to use the Allowance Holder pattern instead of Permit2 for token approvals. Prefer this over the indicative price endpoint when you are ready to actually execute the swap and need guaranteed transaction data. Use over Permit2 quote when your integration or smart contract flow requires standard ERC-20 allowances rather than EIP-2612 signatures.

## Known failure modes

- Insufficient liquidity for the requested token pair or amount returns an error or degraded quote
- Invalid or unsupported token address returns a 400 bad request
- Expired quote if the validity window lapses before execution
- Chain ID not supported by 0x Allowance Holder returns an error
- Missing required query parameters such as sellToken or buyToken returns a validation error
- Payment of $0.01 USDC via x402 protocol required; missing or failed payment returns 402

## How this service works

Get the firm quote for a swap using Allowance Holder to set allowances

## Output

A firm, executable swap quote including the exact output token amount, exchange rate, gas estimate, calldata for the swap transaction, the Allowance Holder contract address to approve, and any protocol fees — all guaranteed for a short validity window.

## 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",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/0x-swap-allowance-holder-firm-quote-33a2072a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent.api.0x.org](https://www.zero.xyz/host/agent.api.0x.org/llms.txt)