Do I need one API that can call multiple model providers?

Not necessarily.

You need one API interface if you want a single consistent way to:

• switch between model providers,
• compare models easily,
• fail over if one provider is down,
• keep your app code simpler.

But you don’t need one unified API if:

• you’re only using one provider,
• each provider has very different features you want to access directly,
• you’re okay maintaining separate integrations.

A practical rule

• Small/simple project: integrate directly with the provider you use.
• Growing product / multi-model strategy: build or adopt one abstraction layer over multiple providers.

Common approaches

1. Direct integrations

   • Your app talks to OpenAI, Anthropic, Google, etc. separately.
   • Best for maximum control.
   • More work to maintain.

2. Unified abstraction layer

   • One internal API in your app, with adapters for each provider.
   • Cleaner app code.
   • Easier to swap models.

3. Third-party router/gateway

   • Use a service that already normalizes multiple model providers.
   • Fastest to implement.
   • Less control / extra dependency.

When a single API is especially useful

• You want provider redundancy
• You need A/B testing
• You plan to use different models for different tasks
• You want to keep your codebase from being tied to one vendor

If you want, I can sketch a simple multi-provider API design for your app.