# Choose your Chain ID Choose a Chain ID that uniquely identifies your chain. It will be used to set up MetaMask later. ``` 98989897 ``` Check that the Chain ID it not taken already using . MetaMask uses ChainList to suggest chain details such as name and currency, and will complain if you use an existing Chain ID. So make sure to choose a new unique Chain ID. If you will deploy your chain for public use, then add your chain to [ChainList](https://chainlist.org/) as well. --- # Agent Instructions: 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.rome.builders/legacy/rome-l2-setup/setup-your-l2/choose-your-chain-id.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.