Be agent for and Tack on

Tack on and be agent for are semantically related. In some cases you can use "Tack on" instead a verb phrase "Be agent for".

Tack on verb - To join (something) to a mass, quantity, or number so as to bring about an overall increase.

Be agent for and tack on are semantically related. Sometimes you can use "Be agent for" instead a verb "Tack on".