You could use placeholders:
in your cron job URL and HTTP Message Body.

When your cron job is executed, EASYCRON_RANDOM will be replaced with a random 12-digit integer, EASYCRON_TIMESTAMP will be replaced with a Unix timestamp, and EASYCRON_CRON_JOB_ID will be replaced with the ID of your cron job.
For example, URL
could finally be when it's fired.

Random integer or timestamp in URL will prevent EasyCron's requests from hitting cache in your proxy or server.