See more info in this discussion
For example, adding labels to a runner will fail:
gh api repos/rajbos/demo-actions/actions/runners/23/labels -f body="{\"labels\":[\"new-gpu\",\"accelerated\"]}"
Response:
{ "message": "Invalid request.\n\nInvalid input: object is missing required key: labels.", "documentation_url": "https://docs.github.com/rest/reference/actions#add-custom-labels-to-a-self-hosted-runner-for-a-repository" } gh: Invalid request.
Invalid input: object is missing required key: labels. (HTTP 422)
Set-Content example.txt '{"labels":["new-gpu","accelerated"]}'
gh api repos/rajbos/demo-actions/actions/runners/23/labels --input .\example.txt