# 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. --- # 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://xai-foundation.gitbook.io/xai-network/en/about-xai/sentry-keys-explained/referee-smart-contract/submission-of-assertions.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.