# Swapping #### Routing It is your responsibility to find the best list of pools for executing a trade. This is equivalent to finding the best route for arbitrage. #### Executing swaps on chain To swap on Ekubo, you must called `ICore#lock`. Ekubo's core contract will call back into your contract with the data you pass, via `IYourContract#locked`. In your lock callback, you execute the swap(s), pay the input, and withdraw the output tokens in no particular order. Note you typically call swap multiple times in a single `locked` callback so you only have to pay the differences. See the Routers on [Starknet](https://github.com/EkuboProtocol/starknet-contracts/blob/main/src/router.cairo) and [EVM](https://github.com/EkuboProtocol/evm-contracts/blob/main/src/Router.sol) for examples of how to execute swaps on-chain. --- # 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.ekubo.org/integration-guides/swapping.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.