I created properties in the request body and tried to use them as parameters in the api url field and the url shows up fine in the preview but when I execute the test, it messes up the url. https://cdn.discordapp.com/attachments/1427384155301220404/1427384155494285443/Screenshot_2025-10-13_at_12.58.26_PM.png?ex=68eeaa96&is=68ed5916&hm=061151f2a9199e56042c15391bc39e364d7a7c4afd9fd8fe0eb703ed61f34920& https://cdn.discordapp.com/attachments/1427384155301220404/1427384155783827596/Screenshot_2025-10-13_at_12.30.34_PM.png?ex=68eeaa96&is=68ed5916&hm=d2fc59793e055a20a20908612141f294cd9bbe9cb56c0a4cbdbd237b2ddb4187& https://cdn.discordapp.com/attachments/1427384155301220404/1427384156068778146/Screenshot_2025-10-13_at_12.30.16_PM.png?ex=68eeaa96&is=68ed5916&hm=039dc9fe97cf125e28b957e000fbc5053a9472bb6d242a4e6eb673102f0c09d0&

Suggestion: To ensure your URL parameters like

{{start}}

,

{{end}}

, and

{{timezone}}

are substituted correctly, define them as top-level parameters in your tool configuration, not just in the request body. For example:

json
{
  "parameters": {
    "start": { "type": "string", "description": "Start time" },
    "end": { "type": "string", "description": "End time" },
    "timezone": { "type": "string", "description": "Time zone" }
  },
  "url": "https://api.cal.com/v2/slots?eventTypeSlug=consultation&username=sailboatai&start={{start}}&end={{end}}&timeZone={{timezone}}"
}

Update your tool config to include these parameters at the top level, then test again. For more, see the [custom tools guide](https://docs.vapi.ai/tools/custom-tools). Source: - [Custom Tools](https://docs.vapi.ai/tools/custom-tools)

It seems like this is a configuration for a custom tool when I am trying to work with the api request tool. Should I be using the custom tool?

I can help you sort this out so your variables work properly when the request runs. This usually happens because the API request tool doesn’t handle dynamic values well, while the custom tool does. You can still make GET requests there without any issue. Could you show me how you set up the variables in your request body? @Ovi1kanobe

Hi Ovi1kanobe, If you are encountering issues with API request tools, particularly with query parameters not being passed correctly, ensure that your request configuration includes all required fields such as

type

,

method

,

url

, and other relevant data according to the [API Reference](https://docs.vapi.ai/api-reference/tools/update). If the

type

is

apiRequest

, the object should include

method

,

url

, and

credentialId

along with any necessary

headers

and

body

. Check if the

rejectionPlan

and

variableExtractionPlan

are properly defined to manage any issues arising during the request execution. Also, keep in mind the

CreateApiRequestToolDto

configuration, and ensure that all required fields are correctly set up, which may impact how the parameters are recognized and executed during tests or actual requests. For detailed steps, you can reference the [SDK documentation](https://docs.vapi.ai/api-reference/tools/update) to ensure your implementation follows the required specifications.