Use Custom Fields in rules

Custom Field variables

Your rule’s actions can reference values in Custom Fields by using Custom Field variables. To reference a Custom Field’s value in an action, use this format: {{%Field Name}}

Example:

when a card is moved to list "Done" by anyone, add member @{{%Tester}} to the card, and post comment "@card Task with priority {{%Priority}} was completed and is ready for testing."

Result:

Let’s say you move a card to the Done list. It’s Priority is set to High, and the Tester Custom Field in that card has the value tacofan in it.

This will add a member to the card with the username tacofan, then post a comment in the card, “@card Task with priority High was completed and is ready for testing.”

The value of a Custom Field used in a rule’s trigger can be referenced later in the rule’s actions using:{customfieldvalue} 

Example: 

when custom field "Priority" is set, for each card linked in the attachments, set custom field "Priority" to {customfieldvalue}

Result:

Let’s say you have three values in the Priority Custom Field: High, Medium, Low. Whenever that field is set in a card, the rule will attempt to set each linked card’s Priority to the same value.

Custom Field arithmetic

When setting the "Number" Custom Field, you can perform basic arithmetic operations such as addition(+), subtraction(-), multiplication(*), and division(/). You can also use numeric constants and parentheses to group arithmetic expressions.

Example:

when a card is moved into list "This Week", set custom field "Total Points" to "{{%Design Points}} + {{%Dev Points}} + {{%QA Points}}"

Result:

When you move a card to the “This Week” list, this will add the numbers in the Design Points, Dev Points, and QA Points Custom Fields, and set the Total Points Custom Field equal to the sum.