Bracket Expressions (Formulas) — {{…}}

TL;DR

• {{expression}}; fields via var("dotted.path") (double quotes, one argument); arguments separated by ;; string literals in double quotes and URI-encoded.
• In formula fields (action inputs, set-variable values, delay due dates) use ONLY the builder function list in §2. Conditions and trigger filters have their own, stricter vocabularies — Automations Conditions (not yet published), Automations Trigger Configuration §4.2.
• The builder type-checks every argument and the arity (§2): eq/gt/gte/lt/lte take NUMBERS only (strings → stringEq, dates → date*); if()'s first argument is boolean. There are no operators.
• No array element access in any form. Project with arrayMap(array;"path"), aggregate with array*. A single-value field can never be filled from an array — ask the user which item.
• Only data from the step's aggregated schema (trigger + ancestors) is in scope (Automations Graph and Data Model §4).

1. Syntax

MUST:

• Every field access is var("path") with ONE argument — {{fieldName}} is not supported.
• Double quotes only (var('x') is an unknown variable to the builder). In JSON escape them: "{{var(\"contact.email\")}}".
• ; between arguments, no leading/trailing/double ;, balanced parentheses. No whitespace outside string literals — {{ concat(… or sum( 1;2) is unreadable to the builder.
• Numbers: plain decimal literals (5, -3, 12.5). Never 0.5, .5, -0.25, 05 or 1e3 — the builder's parser rejects them (conditions, filters, delays and rate limits stop loading). Write divide(1;2) instead. Percentages follow the same rule: 10% of x is divide(x;10) and 15% is divide(multiply(x;15);100), never multiply(x;0.1).
• Path segments may contain hyphens (var("triggered-emails-1.messageId")); a space inside a segment is invalid.
• URI-encode every string literal inside {{…}} exactly as encodeURIComponent does — this is how the builder's panels and the platform store them: "a@b.com" → "a%40b.com", "50%" → "50%25", "New York" → "New%20York", "&" → "%26". Letters, digits and - _ . ! ~ * ' ( ) stay as they are, so uuids and arrayMap paths are unchanged. Do NOT encode var("…") paths (except in trigger filters, where the filter panel encodes the path too — Automations Trigger Configuration) or text outside {{…}}, nor a date-time literal in a formula field (§2). Decode literals when you read an existing automation. Action formula fields display literals as stored, so in string fields keep fixed text outside {{…}} (Hi {{var("contact.name.first")}}, welcome!) rather than in concat("…").

Prefix rules: trigger fields have no prefix; action outputs "<namespace>.<field>" (namespace = the step's namespace, e.g. createTask-1); set variables "setVariable.<key>"; identity enrichment "contact.…" / "member.…". siteInfo.* is not available — don't reference it.

2. Functions the builder renders in formula fields (complete list)

• Math: sum(n;n;…) · subtract(n;n) · multiply(n;n;…) · divide(n;n) · average(n;…) · min(n;…) · max(n;…) · median(n;…) · mod(n;n) · round(n;decimals) · abs(n) → number · eq(n;n) · gt(n;n) · gte(n;n) · lt(n;n) · lte(n;n) → boolean (numbers only)
• Array: arraySize(a) · arraySum(a) · arrayMultiply(a) · arrayAverage(a) · arrayMin(a) · arrayMax(a) · arrayMedian(a) → number · arrayMap(a;"item.path") → array
• Text: concat(s;s;…) · substring(s;start;length) (0-based) · lower(s) · upper(s) → string · stringLen(s) → number · stringEq(a;b) · stringHasSubString(s;sub) · startsWith(s;prefix) · endsWith(s;suffix) · isEmptyString(s) → boolean
• Date: hour(dt) · minute(dt) · year(d) · month(d) · day(d) → number · weekDay(d) → lowercase day name · dateEq/dateBefore/dateAfter(d;d) (calendar date) · dateTimeEq/dateTimeBefore/dateTimeAfter(dt;dt) → boolean · addToDate(d;years;months;days) · subtractFromDate(d;years;months;days) → date-time · now() → date-time string
• Format: toString(v) → string · toNumber(v) → number
• Logic: if(bool;then;else) · and(b;b;…) · or(b;b;…) · not(b) · isEmpty(v) (any value, incl. arrays) → boolean (if → its branches' value)

Arity (write exactly these counts; the builder flags missing and extra arguments for fixed-arity functions): var, not, toString, toNumber, upper, lower, stringLen, abs, isEmptyString, isEmpty, every array* aggregate = 1 · comparisons, round, subtract/divide/mod, arrayMap = 2 · if, substring = 3 (always pass the length) · addToDate/subtractFromDate = 4 · now = 0 · and/or/concat/sum/multiply ≥ 2 · min/max/average/median ≥ 1.

Argument types the builder enforces (convert with toString()/toNumber()):

An encoded date-time literal ("2026-12-25T10%3A00%3A00Z") is not recognized as a date in a formula field — pass a "YYYY-MM-DD" literal or a function, or make the whole field a plain ISO value (§4). This exception is for formula fields only: in a CONDITION the panel itself writes date-time literals encoded and reads both forms (§2 of Automations Conditions (not yet published)).

Semantics: stringEq and stringHasSubString are case-insensitive (normalize with lower() if it matters). Booleans: use the value directly (if(var("isVip");…), not(var("isVip"))), never eq(var("isVip");true).

Never use in a formula field (the builder flags them as unknown functions): toEpoch, arrayFilter, hasSubstring, textWithExpressions, contains, arraySome, arrayEvery, arrayIncludesAnyOf/AllOf/Only, stringContains, numberContains, boolEq, numberEq/numberGt/numberGte/numberLt/numberLte. (Several of these ARE the condition vocabulary — §2 of Automations Conditions (not yet published) — and contains/arraySome the trigger-filter vocabulary.)

Do not exist (never guess): replace, replaceAll, trim, split, join, indexOf, regex/match, ceil, floor, parseInt, parseFloat, random, filter, reduce, sort, switch, loops, try/catch, coalesce, formatDate, formatNumber, formatCurrency, titleCase, add, addDays, equals.

3. if() needs a boolean first argument

Valid first arguments: a comparison (eq, gt, stringEq, dateBefore, startsWith, …), a genuinely boolean field, or and/or/not/isEmptyString/isEmpty.

In number and boolean target fields BOTH branches must return exactly the field's type — a number literal/var/function for a number field. A nested if as a branch counts as "any" and is flagged there: wrap it (toNumber(if(…))) or, for booleans, use and/or. Nested if is fine in string fields.

• ✅ {{if(stringEq(var("status");"active");"Active";"Inactive")}}
• ✅ fallback when the value is missing or empty: {{if(or(isEmpty(var("contact.name.first"));isEmptyString(var("contact.name.first")));"there";var("contact.name.first"))}}
• ❌ {{if(var("status");…)}} when status is a string · ❌ {{if("active";…)}}

4. Field-type rules (what the builder accepts per target field)

• string — Plain text, one expression, or text mixed with any number of {{…}}; no expression may return an array.
• number / integer (incl. string format: number) — Exactly ONE {{…}} covering the whole value, returning a number — or a plain number literal. No surrounding text.
• boolean — Exactly ONE {{…}} returning boolean — or true/false.
• date / date-time — A plain ISO literal without {{}} (2026-12-25T16:00:00Z), or ONE expression: a function (now(), addToDate(…)) or a var. For a date-time field the var must be format: date-time — wrap a format: date var as addToDate(var("d");0;0;0).
• array / object — A literal array/object built field by field, or one {{var("…")}} of the same shape.
• field without dynamicValuesOptions.enabled in the UI schema — Literal only — no {{…}} (Automations Action Configuration §3).

A strict dynamic field requires the exact return type/format. skipActionExpression is "{{true}}" or absent.

5. Arrays — hard limits

• No element access: var("items[0]"), var("items.0.name"), var("items[0].name") are all invalid. Don't invent firstItem/items.id helper paths either.
• Projection: {{arrayMap(var("order.items");"product.name")}} — second argument is a quoted literal path (never $_ or an expression).
• Aggregates: {{arraySize(var("lineItems"))}}, {{arraySum(arrayMap(var("lineItems");"totalPrice.value"))}}. Never arraySum(var("items.price")) — a path cannot cross an array boundary.
• No per-element arithmetic (price × quantity): sum a per-line total field if one exists, else say it is not derivable.
• No lists as text: no join; an arrayMap result can't go into concat or a string field.
• Single-value field from an array → impossible. Ask the user which item or use a user-given value; don't retry array-shaped variants.
• Empty arrays make arraySum/arrayMin/arrayMax/arrayMedian/arrayMultiply fail at runtime.
• Membership tests (does the order contain X) belong in a condition (§3 of Automations Conditions (not yet published)) or, for complex logic, a code condition.

6. Dates

• date* compare calendar dates, dateTime* instants (argument formats: §2). addToDate/subtractFromDate offset by whole years/months/days.
• "Within N days before X": {{dateAfter(var("d");subtractFromDate(var("x");0;0;7))}}. Day differences can't be computed renderably (no toEpoch) — use a DELAY, such a comparison, or a code condition.
• Annual dates (birthdays): never dateEq(var("birthdate");now()). Compare month and day: {{and(eq(month(var("contact.birthdate"));month(now()));eq(day(var("contact.birthdate"));day(now())))}} — in a formula field; as a condition use code or a boolean set-variable (§4 of Automations Conditions (not yet published)).
• Never hardcode a year; derive it: {{dateAfter(var("order_date");concat(toString(year(var("order_date")));"-10-31"))}}. Use year(now()) only when the rule is about the current calendar year.
• Windows crossing New Year (Dec 26 – Jan 4): {{or(and(eq(month(var("d"));12);gt(day(var("d"));25));and(eq(month(var("d"));1);lt(day(var("d"));5)))}}; pick gt/gte from the user's wording.
• Formatting: {{toString(month(var("d")))}}/{{toString(day(var("d")))}}/{{toString(year(var("d")))}} in a string field.

7. Conversions

toString() numbers/booleans before text functions; toNumber() string format: number fields before math; neither converts arrays.

8. Workarounds that stay renderable

• Strip a known prefix: {{if(startsWith(var("price");"%24");substring(var("price");1;subtract(stringLen(var("price"));1));var("price"))}} ("%24" is the encoded "$").
• Title case: {{upper(substring(var("t");0;1))}}{{lower(substring(var("t");1;subtract(stringLen(var("t"));1)))}}.
• Anything needing replace/split/regex/loops → a code condition (for branching) or tell the user it cannot be computed.

9. Self-validation checklist (run on every expression)

1. Parses: balanced {{}} and parentheses, ; separators, double-quoted strings, no whitespace outside strings, no 0.x/.x/exponent numbers.
2. Every function is in §2 (formula fields), the condition table (conditions) or the filter shapes (filters).
3. Arity matches §2 exactly (substring 3, round 2).
4. Argument types match the §2 table: numbers to math/eq/gt…, strings to text functions (toString numbers), dates with the right format, arrays only to array*/isEmpty; if arg 1 boolean and, in number/boolean fields, both branches of the field's type; arrayMap arg 2 a literal path.
5. Every var() path exists in the aggregated schema of THIS step (ancestors only). If the unknown path has an array prefix (items.id where items is an array), element access is inexpressible — stop, don't respell.
6. $_ appears only inside arraySome/arrayEvery predicates (conditions/filters), bare (never var($_) or $_.x).
7. Result type fits the target field (§4); no array into a single-value field.
8. String literals URI-encoded; no single quotes.
9. Final gate: Validate Automation returns no mapping errors — it misses some paths and every builder-only rule above, so steps 1–8 are yours.