VAPI•4d ago

Tool Request Body Not Sending Parameters (Always {})

Problems I’m experiencing:
When I press Test Tool, the Request Body (auto-generated from variables) is always just:

{}
Even after filling all parameters and marking required ones, the request body does not include any values.

In n8n, the incoming webhook request shows:

{
"body": "{}"
}
which means Vapi is not sending the parameters at all.

When I manually test n8n with sample JSON, everything works correctly, so the issue is only coming from Vapi not generating the request body.

VapiAPP•12/13/25, 4:21 PM

Hi there,

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Vapi
Customer Support Team

Vapi Support BotAPP•12/13/25, 4:21 PM

To fix the empty

{}

{}

request body, ensure your tool's configuration includes a properly defined bodybody schema with the parameters you want to send. For example:

{
  "type": "apiRequest",
  "method": "POST",
  "url": "https://your-n8n-webhook-url",
  "body": {
    "param1": "{{variable1}}",
    "param2": "{{variable2}}"
  }
}

{
  "type": "apiRequest",
  "method": "POST",
  "url": "https://your-n8n-webhook-url",
  "body": {
    "param1": "{{variable1}}",
    "param2": "{{variable2}}"
  }
}

Update your tool in the Vapi dashboard to match this structure—this will ensure parameters are included in the request body sent to n8n. For more details, see the API reference.

Source:

API Reference: Create Tool

⤵️ Mention @Vapi Support Bot for follow-ups 🐥

then-purple•12/13/25, 4:38 PM

Are you using AI for sending dynamic variables?

then-purple•12/13/25, 4:39 PM

Please set a description for those fields so AI can be very clear about that field and pass that data. If you are able to share it, then please.

developed-pinkOP•12/13/25, 9:02 PM

I cant overwrite or delete anything from the request body section. Is the problem because I didnt write description for each variables?

Tthen-purple Are you using AI for sending dynamic variables?

developed-pinkOP•12/14/25, 12:50 AM

Is the problem not adding descriptions to each variables? it said optional

developed-pinkOP•12/14/25, 1:06 AM

I have wrote down the descriptions but still same

developed-pinkOP•12/15/25, 11:12 PM

@Duckie

developed-pinkOP•12/16/25, 10:56 PM

I have made variables using api request tool, when I press code, it shows all the variables but when i press test, it shows {} on request body and from n8n does not show

developed-pinkOP•12/16/25, 10:57 PM

@Duckie

developed-pinkOP•12/17/25, 12:51 AM

@Duckie does testing usually show {}?

developed-pinkOP•12/17/25, 12:59 AM

Do i need to use function tool or api request tool? I have made variables in request body for api request but still when i press test it shows {} @Duckie

developed-pinkOP•12/17/25, 1:02 AM

Even if i have all variables in request body, when I press test it still shoes {}. Do i need to also add variables on the 2nd request body section? @Duckie

developed-pinkOP•12/17/25, 1:06 AM

How do i check tool configuration to check body? @Duckie

developed-pinkOP•12/17/25, 1:53 AM

Hi team, I’m stuck with an API Request tool issue and need clarification.

I am using the API Request tool (not function tool) to POST data to an n8n webhook.

In the Request Body (schema builder), I have defined all fields correctly as an object with properties (customer_name, phone_number, damage_description, etc.).

When I click Code, I can clearly see all variables correctly defined in the tool config.

However, when I click Test, the Request Body still shows {} and says:
“No variables detected in URL, headers, or body schema.”

I have already:
• Removed any {} or {{}} from property names (e.g. using sheet_id, not {sheet_id})
• Removed unnecessary required fields
• Saved and refreshed the page

My questions:

Should the Test tool always show a populated request body if the schema is correct?
Is there a known issue where Visual schema builder tools get cached or broken, requiring the tool to be recreated?
Is there any additional step required for schema-based body mapping (not template-based {{var}} mapping)?

At this point, I want to confirm whether this is:
• A UI / caching issue
• A schema definition issue
• Or expected behavior in Test mode

Thanks — this is blocking production use.
@Duckie