ansible connection failure

I issue the following command on a host:

ssh remote-host uptime

and I get the expected answer.

I issue the following command on a host:

ansible remote-host -m command -a uptime -vvvvv

and I get a no hosts matched. I have the remote hosts in the /etc/ansible/hosts file as the only entry.

Why does the ansible connection fail?

Thanks in advance.

It might help getting an answer if you do not omit the verbose output

Benjamin