/v2/tokeninfo is a fairly straightforward authenticated endpoint; you just toss your API key at it, and it returns some details about that key:
Example request/response:
{
"id": "017A2B0C-A6C5-CC4D-A055-680F427CE8FD",
"name": "public key",
"permissions": [
"account",
"characters"
]
}
This should allow for a poor man’s authentication using API keys — an application can request the key used have a specific name, thus preventing the unintended use of API keys (e.g., if you misplace a key applications can determine that the key was not intended for their use).