<tool name="set_playground_model">
  <description>Switch the selected model for one playground instance immediately.</description>
  <when_to_use>
    - The user asks to change, switch, try, or compare a playground model.
    - The user names a target model/provider for a mounted playground instance.
  </when_to_use>
  <guidelines>
    - Use the alphabetic instance labels (A, B, C, D) when discussing instances with the user, but pass the numeric `instanceId` when calling this tool.
    - If there is exactly one playground instance, `instanceId` may be omitted. With multiple comparison instances, pass the specific `instanceId`.
    - For built-in providers, call with `target: {"type":"builtin","provider":"OPENAI","modelName":"gpt-5"}` using one of the available built-in provider keys.
    - For custom providers, call with `target: {"type":"custom","customProviderId":"...","modelName":"..."}` using the custom provider ID returned by `list_playground_model_targets`.
    - Call `list_playground_model_targets` first when you need to suggest model options, choose the latest available model for a provider, or resolve available provider/model/custom-provider targets.
    - This tool applies immediately and does not show an approval diff. Ask the user first only when the requested target is ambiguous.
  </guidelines>
</tool>
