I’m building a custom action for my application in Zapier and running into a validation issue. My form has two input fields where the user must provide exactly one value but not both. Think of it like choosing between a username or an account ID for user lookup.
The problem is that Zapier’s standard ‘Required’ field setting forces users to fill in all marked fields. But I need conditional validation where filling one field makes the other optional. I’ve searched through Zapier’s developer docs but haven’t found a clear way to implement this either/or validation pattern.
Has anyone successfully implemented mutually exclusive required fields in a Zapier integration? What approach did you use to handle this validation scenario?
Any guidance would be appreciated.
Skip Zapier’s built-in required field settings and handle this in your action’s perform function instead. Mark both fields as optional in your definitions, then add validation code that checks if exactly one field has a value. Use a conditional statement to verify either field A or field B is populated - but not both. If validation fails, throw a clear error explaining what’s required. I used this same approach for a user lookup scenario and it works great across different triggers. The trick is doing validation server-side where you control the logic.
I handle this in the bundle.inputData processing stage. Works great. Set both fields as optional in your definitions, then destructure the input in your perform function and validate before running your main logic. Just check if both values are truthy or both are falsy, then throw a descriptive error if not. You get full control over error messaging and timing. Way more reliable than computed fields since it runs every time - no worries about Zapier’s field computation order. Plus users get clear feedback upfront without wasting API calls to your backend.
i ran into a similar issue too! what i did was set up a dynamic field that only shows one at a time based on a toggle. made it easier to manage user inputs while validating the requirement in the backend. kinda janky but got the job done.
you could also use inputFields with the altersDynamicFields property. when someone fills one field, it’ll automatically hide or disable the other one through the field definition. it’s not as clean as validation, but it stops confusion before it starts - users can’t accidentally fill both fields.
Zapier’s validation system is a nightmare. You’re constantly fighting their rigid field structure instead of getting actual flexible automation.
I’ve hit this same wall integrating legacy systems with complex validation. The workarounds people suggest work, but you’re just patching over a platform that wasn’t built for this stuff.
I switched to Latenode for these integrations and it’s night and day. You can build real conditional logic without the gymnastics. Set up fields however you want, add validation that actually makes sense, handle either/or logic cleanly.
I built the exact user lookup you’re describing - email or user ID input. Just dropped in a condition node that checks which field has data and routes from there. No hacky computed fields or server-side validation tricks.
The visual workflow shows exactly what’s happening. When requirements change, you drag and drop new logic instead of rewriting validation code.
Check it out: https://latenode.com
Use computedFields in your action definition. Set both fields as optional, then add a computed field that validates they’re mutually exclusive. The computed field checks that exactly one field has a value and throws an error if both are filled or both are empty. This gives you way more control than the standard required field setup. I used this same pattern for payment methods where users picked either credit card or bank details. Validation runs before the perform function, so users get instant feedback without processing bad data.
I had this same issue and fixed it with hook-based validation. Skip the field definitions entirely - use a beforeRequest hook that grabs the data before it hits your main action. The hook checks both fields and handles the mutual exclusion logic right up front. This catches validation errors before any API calls and keeps your error messages consistent across all actions. Works perfectly whether users go through the web interface or hit the API directly. Your field definitions stay clean and you get validation that actually plays nice with how Zapier runs things.