Using Formulas

Why formulas

Passing data lets you insert values from previous steps into the current step's inputs. Formulas let you transform that data before it gets used — combine two values into one, change the format, do a calculation, fall back to a default when something is empty, or branch on a condition.

If a mention answers "which value goes here?", a formula answers "what should I do with that value first?".

The slash trigger

Place your cursor in any text input and type /. A search popover appears with every available function. Type to filter, click to insert. Each function is inserted as a styled badge with empty argument slots — fill them in with text, numbers, or mentions from previous steps.

<video autoPlay muted loop playsinline src="/resources/using-formulas-slash-trigger.mp4"

</video>

Anatomy of a formula

Once inserted, a formula looks like this in the input:

The function name appears as a pill on the left.
Arguments are separated by semicolons (;), not commas.
A matching pill closes the formula on the right.
A preview panel below the input shows the evaluated result while you edit. If the formula has a type problem (e.g. passing text where a number is expected), the panel shows the error.

You can mix plain text, mentions, and formulas in the same input. The formula's result replaces the badge when the flow runs.

Quoting text values

For text arguments, quotes are optional. The editor accepts both styles and gives you the same result:

Without quotes: combine(John; Smith; -) → John-Smith
With quotes: combine("John"; "Smith"; "-") → John-Smith

Use whichever feels natural. Quotes are useful when:

The text contains a semicolon (which would otherwise be read as the next argument's separator)
You want to be explicit about where the text starts and ends

Empty or whitespace-only values are the one case where quotes are required. Without quotes, the editor treats an empty slot as "no argument" and trims any whitespace, so:

For an empty string, write "" — e.g. coalesce(""; John) → John
For a single space as a separator, write " " — e.g. combine(John; Smith; " ") → John Smith

Without quotes, combine(John; Smith; ) would treat the third argument as missing and fall back to no separator.

Recipes

Combine a first and last name

combine(first_name; " "; last_name) → "Sara Mitchell"

Use combine whenever you need to glue several values together with a separator.

Capitalize a customer name

titlecase(customer_name) → "Sara Mitchell"

Use uppercase if you want everything in caps ("SARA MITCHELL"), or lowercase for the opposite.

Format a date for display

format_date(order.created_at; MMM DD, YYYY) → "Jan 15, 2025"

For a fully written-out date, use format_date_long(order.created_at) → "Friday, January 15, 2025".

Get the first item of a list

first_item(tags) → the first element. Use last_item for the last, or item_at(tags; 2) to pick by index.

Use a fallback when a value is missing

coalesce(customer.preferred_name; customer.first_name; "Friend") → returns the first non-empty value, skipping empty ones.

Use if_empty(value; fallback) for a single fallback, or if_null(value; fallback) when the field could be null specifically.

Branch on a condition

if(order.total > 1000; "High value"; "Standard")

The first argument is the condition. The second is what to return when it's true, the third when it's false.

Strip whitespace and check length

length(trim(user_input)) → tells you how many characters there are after the leading and trailing spaces are removed. Nest formulas freely — the inner one runs first.

Extract an email from a longer string

extract_email(message_body) → returns the first email address found in the text. Use extract_url for URLs.

Round a calculated total

round(subtotal * 1.0825; 2) → 49.99

The second argument is how many decimal places to keep.

Sum a number field across a list

sum(line_items; amount) → adds up the amount field of every item in the list. Use average for the mean, or max_in_list / min_in_list for extremes.

Compute days between two dates

days_between(order.created_at; today()) → the integer day count. Combine with if to flag overdue records.

Map a value through a lookup

switch(country_code; "US"; "North America"; "DE"; "Europe"; "JP"; "Asia") → returns "North America" for "US". Write the pairs inline.

Advanced tips

Nesting formulas

Any formula can take another formula as one of its arguments. Read them inside-out: uppercase(trim(customer_name)) first trims, then uppercases. The hover popover on each badge shows what type each argument expects.

Mixing static text with formulas

You can drop formulas anywhere inside a regular text input. Type some text, insert a formula, type more text. The output is a single string with the formula's result substituted in.

Mixing mentions and formulas

Mentions like {{step.field}} work as formula arguments. Drop a mention into any argument slot and the formula uses the resolved value at runtime.

When the preview shows an error

If you see a red error message under the input, it usually means one of:

Wrong number of values — you have too few or too many arguments. Check the hover popover for the expected count.
Type mismatch — you passed text where a number is expected, or similar. Wrap the value in to_number(...) or to_date(...) if it needs converting.
Unknown function — the function name was renamed or removed. Re-insert it with / to pick a current name.

The flow won't run a step whose formula is in error — fix it before publishing.