So, the request content/body can have "non-sql-like" queries? can it be GraphQL? or even plain English? - of course, assuming that the server knows how to resolve the query.
QUERY /graphql Content-Type: text/graphql {too lazy to write valid gql}
QUERY /elasticsearch Content-Type: application/json {"name": "alice"}
QUERY /my-ai-image-gen Content-Type: text/plain Draw me a picture of a cat