Use phaseo:subagent when the main model should hand off a self-contained task to a smaller or faster worker model during the same request.
The main model calls the Subagent tool with a task description. Phaseo runs the worker model server-side, returns the worker result as tool context, and lets the main model finish the answer.
Quick start
Parameters
The model normally calls Subagent with task_description:
Phaseo also accepts task, prompt, or input as aliases when a model emits a slightly different argument name.
Subagent returns JSON as the tool result:
If the worker request cannot run, Phaseo returns a tool error such as subagent_invalid_request, subagent_max_uses_exceeded, or subagent_request_failed.
Usage and pricing
Subagent calls increment:
The worker model’s tokens are included in total usage and can be priced at the selected worker model’s rates.
Last modified on July 26, 2026