> For the complete documentation index, see [llms.txt](https://docs.usewinter.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.usewinter.com/wallet-api-docs/intro.md). # Intro Winter's custodial wallet is offered for **free** to both businesses implementing Winter's credit card checkout and to customers storing NFTs on Winter's service. However, if the NFT is on Ethereum, it will cost a small gas fee for users to transfer the NFT out of Winter's wallet and into their own wallet. NFTs on Polygon and Solana do not cost any gas fees. Check out some of our [FAQs](< https://winternfts.notion.site/Winter-F-A-Q-cf77158256a042b8814872ce58fe1b58>) here on how to transfer! --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.usewinter.com/wallet-api-docs/intro.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.