{ "$schema": "https://json-schema.org/draft/2020-12/schema", "$id": "https://opensea.io/schemas/ListingItem", "title": "ListingItem", "type": "object", "description": "An item to list for sale", "properties": { "chain": { "type": "string", "description": "Chain of the item (e.g. 'ethereum', 'base')", "example": "ethereum" }, "contract": { "type": "string", "description": "Contract address of the NFT", "example": "0x..." }, "token_id": { "type": "string", "description": "Token ID of the NFT", "example": 1234 }, "quantity": { "type": "integer", "format": "int64", "description": "Quantity to list (use 1 for ERC-721)", "example": 1 }, "price": { "$ref": "#/components/schemas/ListingPrice", "description": "Price per item" }, "start_time": { "type": "string", "description": "Listing start time in ISO 8601 format. Defaults to now.", "example": "2026-05-01T00:00:00Z" }, "end_time": { "type": "string", "description": "Listing end time in ISO 8601 format. Defaults to 30 days from start.", "example": "2026-06-01T00:00:00Z" } }, "required": [ "chain", "contract", "price", "quantity", "token_id" ] }