Bridge: Is it a rule that you must announce the meaning of partners opening bid
I'm going to go just a bit stronger than Ruds here, assuming ACBL rules here.

Unless the ACBL alert chart mentions a specific announcement, you must not announce the meaning of partner's bid unless asked.  That is conveying information to your partner (conveying your interpretation of it), and is explicitly illegal, and may involve a penalty if a director is called.

Further, if it does call for an alert, you must only say "Alert" and no other information unless asked.  Again, providing that information also informs your partner.  (This may vary in high-level tournaments, where separate rooms or screens are used.)

The specific announcements - 1NT range and 1c shortness - are marked in blue on your convention card (indicating an announcement is appropriate).  Anything else - saying "Weak" after a weak 2, for example - is inappropriate.