What placeholders you could use in cron job URL?

You could use placeholders:
EASYCRON_RANDOM
EASYCRON_TIMESTAMP
EASYCRON_CRON_JOB_ID
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
https://www.example.com/?rd=EASYCRON_RANDOM&ts=EASYCRON_TIMESTAMP&id=EASYCRON_CRON_JOB_ID
could finally be https://www.example.com/?rd=123456789000&ts=1613114340&id=123456 when it's fired.

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