Once several teams call models from OpenAI, Anthropic or a cloud provider, costs and data flows become hard to see. A gateway gives IT one point to manage API keys, set spending limits, block sensitive data from leaving and switch a workload to a different model without rewriting each application.
For example, a finance team's document tool and a support team's assistant can share one gateway that logs every request by team. The limit is that a gateway controls traffic, not quality. It will not tell you whether answers are correct, so it complements evals rather than replacing them.