# Midpoint EOAs All on-chain transactions come from a known EOA that your contract can verify. ``` // Checks that the caller is the known EOA. Ensures that your callback is only called when your midpoint returns a response. require(tx.origin == 0xC0FFEE4a3A2D488B138d090b8112875B90b5e6D9, "Invalid EOA"); ``` Live callback EOAs:
ChainAddress
Ethereum Goerli Testnet0xC0FFEE4a3A2D488B138d090b8112875B90b5e6D9
Optimism Goerli Testnet0xC0FFEE4a3A2D488B138d090b8112875B90b5e6D9
Arbitrum Goerli Testnet0xC0FFEE4a3A2D488B138d090b8112875B90b5e6D9
Polygon Mumbai Testnet0xC0FFEE4a3A2D488B138d090b8112875B90b5e6D9
Filecoin Hyperspace Testnet0xC0FFEE4a3A2D488B138d090b8112875B90b5e6D9
Ethereum0xC0FFEE4a3A2D488B138d090b8112875B90b5e6D9
Optimism0xC0FFEE4a3A2D488B138d090b8112875B90b5e6D9
Arbitrum0xC0FFEE4a3A2D488B138d090b8112875B90b5e6D9
Polygon0xC0FFEE4a3A2D488B138d090b8112875B90b5e6D9
Look for 0xC0FFEE when checking an address. --- # 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.midpointapi.com/midpoint-documentation/more-reading/midpoint-eoas.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.