0x Swap Allowance Holder Indicative Price

Use this endpoint when you need a fast, non-binding price estimate for a token swap using the 0x Allowance Holder pattern — ideal for displaying indicative rates in a UI, comparing prices, or deciding whether to proceed to a firm quote. Prefer this over the firm quote endpoint when no commitment is needed yet and you just want to show users an estimated rate. Use the sibling firm quote endpoint when you're ready to execute.

• Token pair not supported — returns 400 with unsupported pair error
• Invalid or missing required query parameters (sell token, buy token, amount) — returns 400 validation error
• Insufficient liquidity for the requested swap size — returns 400 or empty price response
• Chain ID not supported — returns 400
• Payment not made or x402 payment header missing — returns 402 Payment Required
• Rate limiting exceeded — returns 429
• Downstream liquidity provider outage — returns 500 or timeout