> For the complete documentation index, see [llms.txt](https://docs.zerolabs.green/zerolabs-tokenization-module/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.zerolabs.green/zerolabs-tokenization-module/domain-definitions/agreement.md).

# Agreement

**Agreement** is a smart contract that tracks how many **Certificates** were delivered from a **buyer** to a **seller**.

It implements the `onERC1155Received` interface and detects when a Certificate is sent to the agreement, then immediately forwards it to the buyer and accounts for the delivery.

Once the Agreement is fulfilled, it can no longer receive Certificates tokens.

![](/files/XDvq7jyUOkgBXD27Ifu2)