Creates a new job that samples thumbnails from a Mux Video asset, scores them with AI, and selects the best thumbnail candidates. Optional output_steering.scope hard-limits sampling to a time window expressed in seconds while returned timestamps stay absolute to the asset timeline. Other output steering can guide scoring strategy, explicit user intent, audience, and campaign style without changing the response schema.
Arbitrary string stored with the job and returned in responses. Useful for correlating jobs with your own systems.
Mux asset ID.
Maximum number of candidate thumbnails to return (1-5). Defaults to 1.
Curated output_steering controls for execution scope, thumbnail scoring strategy, explicit user intent, audience, campaign style, and scoring priorities. Scope is enforced; other controls guide model behavior but do not guarantee exact output.
Best-effort guidance for what kind of thumbnail candidate should score highest.
Open-ended description of what the user is explicitly looking for in candidate thumbnails. Best-effort guidance only.
Intended audience used as best-effort scoring guidance. Does not change the output schema.
Short description of the campaign/channel thumbnail style to prefer when supported by the frame.
Rubric criteria to emphasize in close calls. Best-effort guidance only.
When true, the highest-scoring thumbnail's timestamp is written to the Mux asset's thumbnail_time once the job completes, making that frame the asset's default poster image. The new thumbnail will appear for some clients sooner than others, depending on local cache settings.
{
"parameters": {
"asset_id": "mux_asset_123abc",
"max_thumbnails": 3,
"update_asset_thumbnail": true,
"output_steering": {
"scope": {
"start_time": 30,
"end_time": 180
},
"selection_strategy": "campaign_thumbnail",
"scoring_priorities": [
"composition",
"brand_fit"
]
}
}
}{
"data": {
"id": "rjob_example123",
"workflow": "find-best-thumbnails",
"status": "pending",
"units_consumed": 0,
"created_at": 1700000000,
"updated_at": 1700000060,
"parameters": {
"asset_id": "mux_asset_123abc",
"max_thumbnails": 3,
"update_asset_thumbnail": true,
"output_steering": {
"scope": {
"start_time": 30,
"end_time": 180
},
"selection_strategy": "campaign_thumbnail",
"scoring_priorities": [
"composition",
"brand_fit"
]
}
}
}
}