The following is accepted by snapcraft without error: client-libs: interface: content content: client-libs read: $SNAP/lib/client When installing the snap, I get the message: ... bad plugs or slots client-libs (read or write path must be set) The above should be instead: client-libs: interface: content content: client-libs read: [$SNAP/lib/client] Or: client-libs: interface: content content: client-libs read: - $SNAP/lib/client snapcraft should tell me that my yaml is invalid instead of silently failing to set the attribute.