> For the complete documentation index, see [llms.txt](https://docs.midpointapi.com/midpoint-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.midpointapi.com/midpoint-documentation/more-reading/startpoints.md). # Startpoints A startpoint is the on-chain interface for your contract to call your midpoint. All calls to a midpoint begin with a call to `callMidpoint()` at the startpoint contract for a given chain.
Midpoint Chain IDChainStartpoint Address
1Ethereum0x8343b2CBE03748f8170b977BD8e1e85098D81B05
5Goerli Testnet0x9BEa2A4C2d84334287D60D6c36Ab45CB453821eB
10Optimism0x0cabEDbDB07C2AFc7D840cF34A2A7CC46DA446BD
137Polygon0x80Ab1b74Fc8E57aE586854A876692D9088e78483
420Optimism Goerli Testnet0xa89c2f3A20cED98cd39AFd0Ab5B207C46Fb2Cdf3
3141Filecoin Hyperspace Testnet0x0705c34AA032354A7966776098E0c12cc5539Bc8
42161Arbitrum One0x0cabEDbDB07C2AFc7D840cF34A2A7CC46DA446BD
80001Polygon Mumbai Testnet0x47a4905D4C2Eabd58abBDFEcBaeB07F1A29b660c
421613Arbitrum Goerli Testnet0x1063051eFe824703E1cf36206A8FA361545E9b54
```solidity event callOracleEvent(uint64 _midpointId, uint256 _requestId, address _contract); event callOracleEventData(uint64 _midpointId, bytes _data, uint256 _requestId, address _contract); uint256 private rollingRequestId; constructor() { rollingRequestId = 0; } function callMidpoint(uint64 _id) public returns (uint256 requestId) { rollingRequestId = rollingRequestId + 1; emit callOracleEvent(_id, rollingRequestId, msg.sender); return rollingRequestId; } function callMidpoint(uint64 _id, bytes calldata _data) public returns (uint256 requestId) { rollingRequestId = rollingRequestId + 1; emit callOracleEventData(_id, _data, rollingRequestId, msg.sender); return rollingRequestId; } ``` --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## 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, and the optional `goal` query parameter: ``` GET https://docs.midpointapi.com/midpoint-documentation/more-reading/startpoints.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. 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.