VAPI•3mo ago

Size limit - VAPI Assistance is sending a truncated argument to the VAPI API Request tool

It seems VAPI Assistance is sending a truncated argument to the API Request tool. Is there a character/payload size limit, and how can I handle this? The payload includes nested JSON (often >1000 chars), and when truncated, no values reach the external webhook. Unfortunately, I don’t have much flexibility to reduce the argument size on my end.

Call ID: 80450359-edda-4e65-8a66-9fd4f0f0534e

Call Time: 09/22/2025 23:15 (IST)

Log Time: Sep 22, 23:17:08.537 (IST)

Vapi Support BotAPP•9/23/25, 6:42 AM

Suggestion:
If your payload is frequently exceeding size limits and getting truncated, consider uploading the large JSON to external storage (like S3 or a file server) and passing only a reference (e.g., a URL or file ID) in your API Request tool call. This keeps the payload small and avoids truncation issues.

{
  "action": "processData",
  "dataUrl": "https://your-storage.com/files/large-payload-123.json"
}

{
  "action": "processData",
  "dataUrl": "https://your-storage.com/files/large-payload-123.json"
}

This approach is recommended for large or nested data structures to ensure reliable delivery to your webhook.

Source:

Custom LLM Tool Calling Integration

⤵️ Mention @Vapi Support Bot for follow-ups 🐥

primary-violetOP•9/23/25, 9:11 AM

@Lordvickthor up to ~2500 characters.

VAPI Assistance → VAPI API Request Tools → External WebhookVAPI Assistance → VAPI API Request Tools → External Webhook

Truncation occurs at: VAPI Assistance → VAPI API Request ToolVAPI Assistance → VAPI API Request Tool and not at VAPI API Request to External WebhookVAPI API Request to External Webhook

VapiAPP•9/24/25, 10:44 PM

We will have to reach out to our team regarding the truncation issue. While we may not be able to support a payload larger than 2500 characters, you might want to consider using a knowledge base of some sort and only pulling the data you need for the one request

Size limit - VAPI Assistance is sending a truncated argument to the VAPI API Request tool

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