Ipinfo

Authentication uses API tokens passed as query parameter or bearer header. A generous free tier (50K requests/month) allows evaluation without payment. The token model is simple — one token per account. There are no complex scoping or permission models. Rate limiting is the primary access control, scaled by plan tier. For agents, this is an excellent access model — minimal setup, generous free tier, and simple token auth.

Documentation is clear and concise. The developer docs cover the API, client libraries, and data types. Examples are provided for common languages. The interactive API explorer lets you test queries immediately. The docs are not extensive but they cover the surface well given the API's simplicity. Data field definitions are clear. The main gap is limited guidance on edge cases (VPNs, proxies, IPv6 behavior).

The API is a single REST endpoint: GET /{ip}/json returns all available data for an IP address. Specific fields can be requested: /{ip}/geo, /{ip}/asn, /{ip}/company. The simplicity is ideal for agents — one call, structured JSON response, no pagination or complex query parameters needed. Batch lookups are available for processing multiple IPs. Client libraries exist for Python, Node.js, Go, Java, Ruby, PHP, and more. The API also supports JSONP and CSV for specialized integrations.

IPinfo provides IP address intelligence: given an IP, it returns geolocation (city, region, country, coordinates), ASN information, hosting/company detection, carrier identification for mobile IPs, and abuse/threat data. For agents that need to contextualize user requests, enforce geographic policies, detect suspicious access patterns, or personalize content by location, IPinfo is a reliable and accurate data source. The service is used by major tech companies and has a strong reputation for data quality.

Error handling is straightforward: invalid IPs return 404, rate limits return 429 with retry-after headers, and auth failures return 403. The responses are consistent and machine-parseable. The main data quality consideration is accuracy variance: IP geolocation is inherently approximate, especially for mobile and VPN traffic. Agents should treat coordinates as approximate (city-level) rather than precise. IPinfo's accuracy is among the best available but the fundamental limitation of IP geolocation applies.