A concrete piece of device data a client can read by uri (MCP resources/list).
resources/list
Optional one-line description.
MIME type of the contents, when known.
Short machine-friendly name (e.g. the file name).
Size in bytes, when known.
Optional human-friendly display name.
Stable identifier passed back to resources/read (e.g. content://media/external/images/media/42).
resources/read
content://media/external/images/media/42