My Voiceflow API block is sending literal variable names like {phone_number} to my Make.com webhook instead of the actual captured values like 07359174024.
I have tried single brackets, double brackets, no brackets, using the Parameters section, adding a Set Variable block before the API call, and rebuilding the API block from scratch. The Capture blocks are working correctly — Voiceflow debug confirms real values are being captured. The problem is the API block body is not hydrating the variables before sending the request.
What is the correct syntax to pass captured variable values in a Voiceflow API block body to a Make.com webhook in 2026?
Error messages or input/output bundles
Voiceflow debug log shows status 400 when no quotes around variables. When quotes are added it sends successfully but with literal text instead of values. Make.com webhook output bundle shows:
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Additional info — when I remove all Input Variables and type the body manually, Make receives phone_number without brackets. When Input Variables are present it receives {phone_number} with brackets. The variable picker in the body shows them in blue/teal. Capture blocks confirmed working in Voiceflow debug.
Hi! I’m the (Company Name) Virtual Consultant. I’m here to check if your roof qualifies for the 2026 Solar Incentives and calculate your projected ROI in under 60 seconds.
To start, do you own the property?
Yes or No?
Yes
Main Flow
To give you an accurate savings estimate, what does your average monthly electricity bill look like? (e.g. £150)
£150
Main Flow
Got it. And how’s your roof looking? Is it mostly free from heavy shade like trees or nearby buildings?"
clear roof, no shade
Hi Michal, here is my full flow script and screenshots of my Set Variable block and Listen/Capture block. The capture blocks are correctly saving to the variables. The Set Variable block is mapping them before the API call. But the API block body is still sending literal text like {phone_number} instead of the real value. Can you see what’s wrong with my setup? Also ignore Main Flow spam between scripts it’s just the name of my workflow.
Main Flow
Nice! What’s your postcode? I’ll check what specific incentives and grid programs are available in your area?
rm13 8jw
Main Flow
Checking availability in your area…
Good news — it looks like your property could be a strong fit for solar based on your area. I’m just finalizing your custom ROI report now…
We’ve only got a few survey slots left this week in your area, and they’re filling up fast.
Want to grab one of those quick slots to see exactly how much you could be saving with the current solar incentives and grid programs?
Book my free survey
Main Flow
Excellent. What’s the best mobile number to send your confirmation to?
07359174024
Main Flow
All set! I’ve sent your details over to the team. One of our specialists will be in touch shortly to walk you through your custom report. Have a great day!‘’
What is your goal?
What is the problem & what have you tried?
Error messages or input/output bundles
