When a declarative agent, such as a custom "Researcher agent," is published and accessed from within the Microsoft 365 user interface, it is in a deployed state for end-user consumption. The Microsoft 365 client does not provide authoring controls to alter the agent's foundational behavior. You cannot change its base instructions, add new starter prompts, or delete existing suggested prompts directly from the M365 chat interface. To make any structural or behavioral modifications, the developer or administrator must return to the original authoring environment (e.g., Microsoft Copilot Studio), edit the configuration parameters there, and republish the agent.

Microsoft Learn Documentation: Overview of declarative agents for Microsoft 365 Copilot. Section: "Authoring and Publishing". This document specifies that the creation and modification of declarative agent configurations (instructions, prompts, knowledge) occur exclusively within Copilot Studio or via the Teams Toolkit, not the M365 client UI.

Microsoft Learn Documentation: Manage Microsoft Copilot Studio agents in Microsoft 365. Section: "Edit an existing agent". It dictates that to update an agent deployed to M365, makers must open the agent in Copilot Studio, make the necessary changes, and select "Publish" again.