The docs mention that it can be accessed via CLI, but there are no samples for CLI in the docs, only PowerShell.
Any advice on where to get started?
You can find the details on how to manage Cognitive Services in the Cognitive Services Azure CLI documentation.
As usual with Azure Government:
az cloud set --name=AzureUSGovernment
Here's a quick sample on how to get going:
az cloud set --name AzureUSGovernment
az login
az group create -n cogstestrg -l usgovvirginia
az cognitiveservices account create -n cogstestcv -g cogstestrg --sku S0 --kind ComputerVision -l usgovvirginia
az cognitiveservices account show -g cogstestrg -n cogstestcv
az cognitiveservices account keys list -g cogstestrg -n cogstestcv
#Make sure you REPLACE_WITH_YOUR_KEY in the curl command below using the key from the previous command
curl -v -X POST "https://virginia.api.cognitive.microsoft.us/vision/v1.0/analyze?visualFeatures=Categories,Description,Color&details=&language=en" -H "Content-Type: application/json" -H "Ocp-Apim-Subscription-Key: REPLACE_WITH_YOUR_KEY" --data-ascii "{'url' : 'http://upload.wikimedia.org/wikipedia/commons/3/3c/Shaki_waterfall.jpg'}"