Some validations can't be done inside WeTransform alone. Is this VAT number real? Does this customer ID exist in your database? Is this delivery address valid? These checks require calling an external system — in real time, during the transformation.
That's what Power Functions are for.
⚡ What is a Power Function?
A Power Function is a rule action that calls an external API during the transformation process. WeTransform sends the relevant data to your external system, waits for the response, and populates the result directly into your file, viewable on the Finalize screen.
You choose when to trigger it, on which column, and under which conditions. The result appears automatically, like any other rule output.
🏭 Real-world examples
🔍 VAT validation — for each row, send the VAT number to a business registry API. If invalid, flag the row as an error before submission.
📍 Address lookup — send an address to an external API to validate a delivery address against a mapping service. Correct misspellings or flag unrecognized addresses automatically.
🪪 Customer ID check — verify that a customer_id in the incoming file actually exists in your CRM or database before accepting the file.
🚗 License plate verification — check that a plate number corresponds to a real registered vehicle, using a government or third-party API.
⚙️ How to use a Power Function
Once you've developed your power function, it becomes available for your users, natively in WeTransform.
Power Functions are available as a rule action in the Rules editor. Open the Rules editor, create a new rule, and in the THEN section, open the action dropdown and select "Power functions". You'll see the list of available functions — both native ones and any custom ones set up in your account.
🔑 Some functions require an API key. Native functions like "Generate content with AI" require an OpenAI API key, and "Send an email" requires a Sendgrid key. Custom Power Functions you build yourself will require the API key for the external system you're calling. These are configured in your account settings.
✅ What happens after the function runs?
The result of the Power Function appears directly in your Finalize table — no manual step needed. If the function returns an error or flags a row, it will appear as a regular error in Finalize, with the same correction options as any other error.
🛠️ Building your own Power Function
Custom Power Functions are built by your development team using the WeTransform API. They follow a simple pattern: WeTransform calls your endpoint with the row data, your system processes it and responds, WeTransform writes the result back into the transformation.
For the full technical documentation, visit api.wetransform.com/en/documentation/power-functions.
👉 What to do next