Writing a “local check” script might be even easier than an mrpe check, without the need to include this in a separate .cfg file.
Something as simple as:
#!/bin/sh
if type lsb_release >/dev/null ; then
echo "0 lsb_release - $(lsb_release --short --description)"
fi
exit 0
Just put it into /usr/lib/check_mk_agent/local/ (and set the executable bit: chmod +x ... ).
Should be discovered as a new local check named “lsb_release” without perfdata, always OK.