Service Tiers

Service Tiers

The service_tier parameter lets you control cost and latency tradeoffs when sending requests through OpenRouter. You can pass it in your request to select a specific processing tier, and the response will indicate which tier was actually used. Your request is billed at the actual served tier’s rate.

Using Service Tiers

Pass service_tier as a top-level parameter in your request body. Supported values are flex (lower cost, higher latency) and priority (faster, higher cost). The example below requests the flex tier from OpenAI’s gpt-5 for a 50% discount in exchange for higher latency and lower availability.

$
curl https://openrouter.ai/api/v1/chat/completions \
>
  -H "Authorization: Bearer {{API_KEY_REF}}" \
>
  -H "Content-Type: application/json" \
>
  -d '{
>
    "model": "{{MODEL}}",
>
    "service_tier": "flex",
>
    "messages": [
>
      { "role": "user", "content": "What is the meaning of life?" }
>
    ]
>
  }'

The service_tier parameter is also accepted on the Responses API and the Anthropic Messages API — see API Response Differences below for where the response field is returned in each.

$
curl https://openrouter.ai/api/v1/messages \
>
  -H "Authorization: Bearer <OPENROUTER_API_KEY>" \
>
  -H "Content-Type: application/json" \
>
  -d '{
>
    "model": "openai/gpt-5",
>
    "service_tier": "flex",
>
    "max_tokens": 1024,
>
    "messages": [
>
      { "role": "user", "content": "What is the meaning of life?" }
>
    ]
>
  }'

Supported Providers

The following providers support flex and priority for select models. The response’s service_tier field reports which tier was actually used.

OpenAI

• Possible response values: default, flex, priority

Learn more in OpenAI’s Chat Completions and Responses API documentation. See OpenAI’s pricing page for details on cost differences between tiers.

Google (Vertex AI)

• Possible response values: standard, flex, priority

Learn more in Google’s Flex and Priority documentation.

Google (AI Studio)

• Possible response values: standard, flex, priority

Learn more in Google’s Flex and Priority documentation.

API Response Differences

The API response includes a service_tier field that indicates which capacity tier was actually used to serve your request. The placement of this field varies by API format:

• Chat Completions API (/api/v1/chat/completions): service_tier is returned at the top level of the response object, matching OpenAI’s native format.
• Responses API (/api/v1/responses): service_tier is returned at the top level of the response object, matching OpenAI’s native format.
• Messages API (/api/v1/messages): service_tier is returned inside the usage object, matching Anthropic’s native format.