I have created an API request tool. It have a one mandatory body param. But it is empty on the test UI and while integrated to the agent this field is not filled. On calling this tool agent also refuse to fill up the field and request returns an error. https://cdn.discordapp.com/attachments/1452080018204266608/1452080019290460272/image.png?ex=697d3e66&is=697bece6&hm=d16e446ca70b0aaeaa9be3b863e93d7b0f274191e23131a3c5f1bcb432419e31&

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Thank you for sharing the details of your issue. Based on the information provided, it appears that your API request tool requires a mandatory body parameter (

id

), but this field is not being filled in the test UI or when integrated with the agent, resulting in an error when making the request. Unfortunately, I do not have additional information on why the test UI or agent is not populating the

id

field, or how to resolve this specific issue. If you have access to further configuration options or logs, reviewing those might help identify why the parameter is not being set. If you have any more details or specific questions, feel free to share them!

Hi RinatKurmaev, Please try these quick checks and workarounds: 1. Verify tool parameters in the tool config - Confirm the parameter exists under

parameters

(type: object → properties) and is marked required. - If using the API Request tool, check that variableExtractionPlan.schema.properties is populated (dashboard currently may not sync it automatically). 2. Test with raw JSON/defaults - In the Test panel switch to raw JSON (or paste a sample body) including the required "id" to confirm the endpoint works. - Add a default value for

id

in the schema to see if the Test UI uses it. 3. Test via CLI or an actual call - Use the CLI or make a real test call (dashboard "Call"/assistant test) — the Test UI is known to show {} sometimes while real calls include toolCallId and proper population. See Debugging quick checks: https://docs.vapi.ai/debugging 4. Workaround: create as Custom Tool - If the API Request tool’s Test UI won’t populate fields, create the same tool as a Custom Tool (this has helped other customers). See Tools Create/Update reference: https://docs.vapi.ai/api-reference/tools/create and https://docs.vapi.ai/api-reference/tools/update 5. If problem persists — collect logs - From Observe > Call Logs grab a failing call ID and timestamp and share it here so we can inspect whether the LLM produced the id and whether it was dropped before the tool call. Dashboard troubleshooting steps: https://docs.vapi.ai/debugging

> Confirm the parameter exists under parameters (type: object → properties) and is marked required. Yes they do { "id": "3cc8ba49-c6c2-4227-baa8-a23c074237c3", "createdAt": "2025-12-21T01:47:47.229Z", "updatedAt": "2025-12-21T01:50:30.817Z", "type": "function", "function": { "name": "get_balance", "strict": true, "description": "the tool to get the client balance by their last four digits of the SSN ", "parameters": { "type": "object", "properties": { "ssn": { "description": "the last four digits of the client SSN", "type": "string", "default": "5555" } }, "required": [ "ssn" ] } }, "messages": [ { "type": "request-start", "blocking": false } ], "orgId": "ad1afaa0-332f-42c3-b5aa-2be10a9136fd", "server": { "url": URL_HERE, "timeoutSeconds": 20 }, "async": false } The test panel doesn't fill up the body of the request

Could you please try testing a call using your tool with the same parameters? There have been some recent platform updates, and we’d like to confirm whether the issue is still occurring. If the issue persists, please share the call ID here so we can investigate further.