Using the below example I was unable to access the priority tier for the Agent Platform API. This is illustrated by the response field ‘traffic_type’ = ‘ON_DEMAND’.
Tried the minimum viable use case on the website:
curl -X POST
-H “Authorization: Bearer $(gcloud auth print-access-token)”
-H “Content-Type: application/json; charset=utf-8”
-H “X-Vertex-AI-LLM-Request-Type: shared”
-H “X-Vertex-AI-LLM-Shared-Request-Type: priority”
“https://aiplatform.googleapis.com/v1/projects/PROJECT_ID/locations/global/publishers/google/models/gemini-2.5-flash:generateContent” -d
$‘{
“contents”: {
“role”: “user”,
“parts”: { “text”: “PROMPT_TEXT” }
}
}’
The call returned the following:
“candidates”: [
{
“content”: {
“role”: “model”,
“parts”: [
{
“text”: “Hello there! How can I help you today?”
}
]
},
“finishReason”: “STOP”,
“avgLogprobs”: -0.45475735664367678
}
],
“usageMetadata”: {
“promptTokenCount”: 1,
“candidatesTokenCount”: 10,
“totalTokenCount”: 33,
“trafficType”: “ON_DEMAND”,
“promptTokensDetails”: [
{
“modality”: “TEXT”,
“tokenCount”: 1
}
],
“candidatesTokensDetails”: [
{
“modality”: “TEXT”,
“tokenCount”: 10
}
],
“thoughtsTokenCount”: 22
},
“modelVersion”: “gemini-2.5-flash”,
“createTime”: “2026-07-29T10:31:34.164297Z”,
“responseId”: “htZpasmDCrnyxs0PubWNyAM”
}