> ## Documentation Index > Fetch the complete documentation index at: https://docs.rockapi.ai/llms.txt > Use this file to discover all available pages before exploring further. # AI API gateway: one interface for OpenAI, Anthropic, Google, and OpenAPI services > Learn what an AI API gateway is, when developers need one, and how Rock API centralizes model access, API keys, billing, and OpenAI-compatible requests. # AI API gateway: one interface for OpenAI, Anthropic, Google, and OpenAPI services An **AI API gateway** gives developers one stable interface for sending requests to multiple AI model providers. Instead of wiring separate accounts, SDK settings, API keys, invoices, and usage dashboards for every provider, your application calls one base URL and the gateway handles access to the enabled models. AI API gateway architecture showing one application calling Rock API to reach OpenAI Anthropic Google and OpenAPI services Rock API is an AI and OpenAPI marketplace for teams that want a single OpenAI-compatible entry point for model usage and a buyer workflow for third-party APIs. It is useful when you already use OpenAI-style SDKs, want to test models from OpenAI, Anthropic, and Google, and need clearer billing across a team. ## What an AI API gateway does An AI gateway sits between your application and upstream providers. Your code sends a request to the gateway, the gateway authenticates the request, routes it to the selected provider or API service, and returns the response in a format your client can consume. For AI model usage, the highest-value gateway features are: * A single API key for supported models and services. * One base URL for OpenAI-compatible clients. * Centralized prepaid balance and usage visibility. * Access to multiple model families without rewriting your application. * A clean migration path from direct provider API calls. ## When a unified AI API makes sense Use a unified AI API when your team is moving from experiments to production. The cost of maintaining separate provider integrations usually shows up later: duplicated key management, provider-specific billing, inconsistent request formats, and fragmented usage reporting. Rock API is especially practical for: | Use case | Why a gateway helps | | ------------------------------ | -------------------------------------------------------------------------------------------- | | SaaS products with AI features | Keep one integration while choosing different models by task. | | AI agents and chatbots | Test model behavior without changing the application architecture. | | Startup teams | Reduce integration overhead and control model spend earlier. | | API buyers | Discover, subscribe to, test, and operate third-party OpenAPI services from one marketplace. | ## AI API gateway vs direct provider integration Direct provider integration is simple when you use one provider and one model. It becomes harder when your product needs multiple models, multiple environments, and team-level cost control. | Decision point | Direct provider APIs | AI API gateway | | --------------------- | ------------------------------ | --------------------------------------- | | API keys | One key per provider | One Rock API key for supported access | | Billing | Separate accounts and invoices | Centralized prepaid balance | | SDK migration | Provider-specific changes | OpenAI-compatible format | | Model switching | More code and account setup | Change model names within one interface | | Marketplace discovery | Not included | Buyer and seller workflows for APIs | ## FAQ ### What is the difference between an AI API gateway and an AI API aggregator? An aggregator focuses on access to multiple models or APIs. A gateway usually adds operational controls such as authentication, billing, usage tracking, routing, and a stable API surface. In practice, buyers often search for both terms when they want one place to manage AI model access. ### Is an AI API gateway only for enterprise teams? No. A gateway can help small teams earlier because it reduces setup time and makes model spend easier to understand. Enterprise teams usually care more about governance, procurement, and compliance review. ### Does Rock API replace the OpenAI SDK? No. Rock API works with OpenAI-compatible clients. In many cases, you keep the SDK and change the base URL and API key. ## Next step If your main goal is cost reduction, read [Cheap AI API: how to lower LLM token costs](/blog/buyers/cheap-ai-api). If your main goal is migration, read [OpenAI-compatible API migration guide](/blog/buyers/openai-compatible-api).