What
A cloud session is a session running on remote machines. When one is created with a deviceBinding, meaning it is tied to a particular device, the request now lists four MCP tools as not allowed. MCP (Model Context Protocol) tools are extra tools supplied by a connected server, and these are named mcp__<server>__ followed by the tool name:
device_bashdevice_list_dirdevice_stage_filesdevice_commit_files
Any tools the caller has already blocked through disallowedTools go into the same list, which is sent as disallowed_tools.
Why
In a session bound to a device, Claude cannot call these four device tools. Tools you block yourself stay blocked alongside them.