> +         (add-before 'configure 'chdir
> +           (lambda _
> +             (chdir "subprojects/groovy-jmx")))

#t

> +    (description "This package contains the JMX extension of Groovy, for
> +management and monitoring JVM-based solutions.")))

management and monitoring of JVM-based solutions
                          ^^

or

managing and monitoring JVM-based solutions
^^^^^^^^

LGTM!