Several product teams call model providers directly. What does introducing an AI gateway buy, and what does it cost?

What it buys

• Cost attribution and control. Per-team and per-feature spend, budgets, and the ability to see which feature is expensive. Model spend has no natural ceiling and grows silently, and attribution is what changes behaviour.
• Provider abstraction and failover. When a provider is degraded or rate-limiting, requests route elsewhere. Without a gateway, each team implements this separately or not at all — and "not at all" is the common case.
• A single place for guardrails: input filtering, output checking, prompt-injection detection, and redaction of sensitive data before it leaves the boundary. Implementing these in ten places produces ten different levels of protection.
• Caching, which for repeated or similar prompts is a direct cost reduction.
• Observability: latency, token usage, error rates and quality signals in one place, with the ability to compare providers on the same traffic.
• Rate limiting per team, so one runaway feature does not exhaust a shared provider quota.

What it costs

• A hop on the request path, with its own availability. A gateway that is down is every AI feature down, so it must be simple, well-operated and statically stable.
• Lowest-common-denominator abstraction. Provider-specific capabilities — structured output modes, caching semantics, tool-calling differences — are either lost or leak through, and the leak defeats part of the purpose.
• A team to own it.

The judgement

Introduce it when the second or third team starts calling providers directly, not before and not much after. Earlier is premature abstraction over a single use case; later means retrofitting across teams that have each built their own conventions.

The strongest single argument is cost visibility, because model spend is the fastest-growing and least attributed line in most organisations adopting these systems — and the gateway is the only place it can be measured without asking every team to instrument themselves.

The escape hatch

Allow direct provider access for teams with a genuine need, recorded as an exception. A gateway with no escape hatch is bypassed by the team with the unusual requirement, and then the governance it provides has a hole nobody knows about.