OpenAI API vs Anthropic API

OpenAI has the bigger toolbox. Anthropic has the more reliable model.

For most teams the API choice is downstream of the model choice. But the surrounding tooling does matter.

	OpenAI API	Anthropic API
Models	GPT-4o, 4.1, o1, o3, plus image and voice models.	Claude Sonnet 4, Opus 4, Haiku.
Multimodal in API	Vision, audio (TTS, STT, Realtime), image gen (DALL-E).	Vision (images and PDFs).
Function calling	Mature. Parallel calls. Strict schema mode.	Mature. Excellent schema adherence.
Streaming	Yes, with Realtime support.	Yes.
Caching	Automatic prompt caching for prefixes ≥1024 tokens.	Explicit cache control. More flexible.
Batch API	Yes. 50% discount, 24h SLA.	Yes. 50% discount.
Rate limits	Usage-tier ramp. Paid tiers scale fast.	Slower default ramp; need to ask for higher.
SDKs	Python, Node, Go, Java, .NET.	Python, TypeScript.

Pick OpenAI when: you need voice or image generation, you want broader SDK support, or you're building agents.

Pick Anthropic when: you need the most reliable function-calling and the highest-quality writing/code review.

Bottom line

Production systems should be model-agnostic anyway. Use both. Route by task. Track quality and cost per route.

We do this for clients every week. Bring us the workflow, we'll bring the architecture.

Glossary