> For the complete documentation index, see [llms.txt](https://docs.fly.trade/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fly.trade/flycn/developers/deprecated-magpie-contracts/magpieaggregator-diamond-proxy/aggregator.md).

# Aggregator

The aggregator is used to perform on-chain and cross-chain swap. The aggregator also lets the user estimate gas for a particular kind of swap. And also to check if a transfer key has been used.