As
@sravangoud implied, GraphQL is a bit more formal with regards to input than your average RESTful service. Here's an example of a simple public service I created a quick Web API service definition for as a test:

Note, the query portion of the body must be created essentially as a string with embedded newlines. You can test against this same public service and view it's schema here:
https://countries.trevorblades.com/Cheers,
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Eric Wilson
Director, Integrations and Enablement
Blue Prism Digital Exchange
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