One key, every API
Use the same secret API key for postal, IP, email, phone, and the rest of the API, with one team managing access and usage.
Adding an IP lookup to an app that already uses postal data shouldn't require another account or another set of credentials. I want these APIs to feel like parts of the same service, because they are.
A secret API key works across the endpoints. With your key stored in PARSEAPI_KEY, these calls all use the same header:
curl -H "X-API-Key: $PARSEAPI_KEY" "https://api.parseapi.com/postal/33139?country=US"
curl -H "X-API-Key: $PARSEAPI_KEY" "https://api.parseapi.com/ip/8.8.8.8"
curl -H "X-API-Key: $PARSEAPI_KEY" "https://api.parseapi.com/email/name@example.com"
curl -H "X-API-Key: $PARSEAPI_KEY" "https://api.parseapi.com/phone/+14155552671"
Authorization: Bearer works too if that's what your HTTP client already uses.
The key belongs to a team, and that team's plan determines its access and allowances. Ordinary lookups share the team's request pool. Products with a separate verification allowance still use the same key. You don't provision another credential to use them.
You can see the usage together in the dashboard and manage the credential in one place. When you add another endpoint to the app, the setup is already done. The work left is deciding what to do with the response.