# Model Filtering

`ai-gateway-model-filtering-v2`

Model Filtering decides which models an app may use and creates the model
selection the rest of the chain works from. Without it, an app can reach any
model offered by the providers assigned to its [team](../teams.mdx).

Configure each capability—completions, embeddings—in one of two modes. The modes
are mutually exclusive per capability.

- An **allow list** exposes a curated set of models. The first entry is the
  default when a request names no model.
- A **block list** permits every available model except the ones named. Each
  request must name its model, because a block list supplies no default.

Models are written as `providerName/model`, where `providerName` is the provider
name configured in your gateway—for example `openai/gpt-5`.

## What a rejected request gets

| Request                                          | Response                      |
| ------------------------------------------------ | ----------------------------- |
| A model the rules don't allow                    | `403`, listing what's allowed |
| No `model` named, in block list mode             | `400`                         |
| A capability the policy doesn't configure at all | `403`                         |
| A provider name that isn't in the catalog        | `400`                         |

Rejections are returned as problem details, and the `detail` names what the
caller should have sent—the allowed models for a blocked model, or the gateway's
configured provider names for an unrecognized one. The
[Akamai AI Firewall](./akamai-ai-firewall.mdx) is the exception among the
policies here: it answers in the provider's own error format instead.

Place Model Filtering first in the chain—it creates the model selection that
[Fallback Model](./fallback-model.mdx) and [Budgets and Costs](./metering.mdx)
build on.

For the portal workflow see
[Restricting models](../managing-apps.mdx#restricting-models); for every option
see the [generated reference](/policies/ai-gateway-model-filtering-v2-inbound).
When model selection needs logic instead of a list, see
[Dynamic model routing](../cookbooks/dynamic-model-routing.mdx).