I've had a fair number of users send me feedback saying this isn't the best practice, I should use tokens in HTTP auth headers or use various other auth schemes.
But from my perspective, for an API that is offering really very simple functionality, using HTTPS & not handling user data etc. then this is quite OK - especially when you consider the benefits of how simple it is to get up and running.
I have quite a few university course conveners include my free API in their entry level CS classes because it's super fast & rewarding for students to go from finding my API to then having a JSON object in their code, no tokens required!