> For the complete documentation index, see [llms.txt](https://xai-foundation.gitbook.io/xai-network/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://xai-foundation.gitbook.io/xai-network/kn/about-xai/sentry-keys-explained/referee-smart-contract/submission-of-assertions.md).

# Submission of Assertions

The contract allows Sentry Nodes to submit assertions to a challenge. This function can only be called by the owner of a Sentry Key or addresses they have approved on this contract. The function checks if the challenge is open for submissions and if the Sentry Key hasn't already been submitted for this challenge.