The web Claude wouldn't tell me, but Claude Code had no reservations:
EndConversation (deferred tool): use only for sustained user abuse directed
at the assistant, or when the user explicitly asks to see it demonstrated.
Load the full guidance via ToolSearch("select:EndConversation") before using
it.
There's a much more detailed set of instructions that are provided when the agent goes to invoke it:
I learned a ton of useful things about ChatGPT Work by having it dump out its tool descriptions the other day: https://codex-tool-reference.simonw.chatgpt.site/