The GraphQL Admin API has a single endpoint:
POST https://adminapi.mementopayments.com/v1/graphql.json
query {users {idfirst_namelast_namefunding_sources {idbalances {currency {code}amount_in}}}}
A successful query results in a response like this:
{"data": {"users": [{"id": "cf767154-c863-488e-93e5-ed1d50561fb8","first_name": "Test","last_name": "McTesterson Jr.","funding_sources": ["id": "7784759a-860e-4d62-a61a-7010d3e7f9d9","balances": [{"currency": "USD","amount": 329.50}]]}]}}