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When you send a request to https://gateway.ngrok.ai, the model field tells the AI Gateway which model to call. Use a model ID when you want the gateway to resolve the provider from the model catalog. Use provider:model when you want to choose the provider yourself.

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Use a model ID

Use a model ID when you know which model you want to call and don’t need to force a specific provider.
The gateway looks up gpt-4o in the model catalog and finds every provider that serves it. It tries the model author’s own provider first (OpenAI here), then any reseller that serves the same model, such as OpenRouter. Providers your access key can’t use drop out.

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Route to a specific provider

Use provider:model when you want predictable routing or need to avoid ambiguity between model names.
In this example:
  • openai is the provider ID.
  • gpt-4o is the model ID.
Use this format when you have more than one provider configured, want to call a custom provider, or want the request to go to one specific upstream.

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Let ngrok.ai choose

Set model to ngrok/auto to let ngrok.ai pick a model for each request, starting with the cheapest one that fits the prompt. See Automatic model selection.

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Use a custom provider model

Custom providers use the same provider:model format. In this example, my-ollama is your custom provider ID and llama3.2 is the model ID configured on that provider.

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Check model capabilities

Before choosing a model, check the model catalog for:

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Keep access rules in mind

The request can only use providers and models allowed by the access key configuration assigned to the access key. If you need to limit what a client can call, see Restrict providers and models.

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Next steps