power-automate-expression-syntax

name	power-automate-expression-syntax
description	Write, validate, and debug Microsoft Power Automate expressions. Use for Workflow Definition Language expressions in cloud flows, dynamic content, runAfter conditions, null-safe property access, variables, trigger/action outputs, date/string/array functions, and for deciding when Power Fx applies only to desktop-flow or other Power Platform formula surfaces.

Power Automate Expression Syntax

Power Automate cloud flows use Workflow Definition Language expressions. Power Fx is a separate formula language and is not the default for cloud-flow JSON.

Workflow

1. Identify the expression host:
   • Cloud-flow action/condition/JSON: WDL expressions.
   • Desktop flow formula mode: Power Fx.
2. For cloud-flow expressions, read references/cloud-flow-expressions.md.
3. For desktop-flow Power Fx, read references/power-fx-desktop-flows.md.
4. Validate against live run inputs where possible; expression errors are often data-shape errors rather than syntax-only errors.

Cloud-Flow Guardrails

• Use @{...} inside string interpolation and @... when the whole value is an expression.
• Prefer null-safe access with ?[] for optional action outputs.
• Use exact action names in outputs('Action_Name'), body('Action_Name'), and actions('Action_Name').
• Avoid copying expressions from rendered docs without checking quotes and invisible characters.
• Confirm a function exists in power-automate-reference (the complete WDL namespace) before using it — the namespace is closed; do not invent functions.