/usr/bin/mono-api-info is in mono-devel 2.10.8.1-1ubuntu2.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 | #!/bin/sh
exec /usr/bin/mono $MONO_OPTIONS /usr/lib/mono/4.0/mono-api-info.exe "$@"
|