I was chatting with a customer yesterday on various automation topics and one of the questions was about automating the vSAN Data Migration Pre-Check capablitity, which is available in the vSphere UI under vSAN Cluster->Monitor->vSAN->Data Migration Pre-check as shown in the screenshot below.
The specific vSAN API that you will need to use is both the VsanPerformResourceCheck to perform the operation and then VsanGetResourceCheckStatus to retrieve the results as the operation can take some time depending on the size of your environment.