Metadata for an OData service can be fetched by requesting the service document or service metadata using a GET request.

Service Document

The service document returns a list of all the available entities in a schema in the request payload. To fetch the service document, issue a GET request for the data source's service root.
<server>:<port>/api/odata/<hdp_data_source>
For example: 
https://MyServer:8443/api/odata/myds/

Service Metadata

Fetching service metadata returns a description of the data model for the service, including the names, properties, data types, and relationships for all entities in the schema. To fetch service metadata, issue a GET request for the data source's service root with /$metadata appended to the path:

<server>:<port>/<hdp_data_source>/$metadata

For example: 

https://MyServer:8443/api/odata/myds/$metadata