VAPI•2mo ago

VAPI Tool Not Being Called - BYO Phone Number Issue

Issue
Custom async function tool returns "Unknown tool: undefined" during live calls instead of
calling the configured webhook.

Setup

BYO phone number (Zadarma SIP)
Tool type:
```
function
```
function
```
function
```
function
,
```
async: true
```
async: true
```
async: true
```
async: true
Tool has
```
server.url
```
server.url
```
server.url
```
server.url
configured
Tool is in assistant's
```
model.toolIds
```
model.toolIds
```
model.toolIds
```
model.toolIds
array
GPT-4o modelWhat I See in Call Transcript```AI calls: load_user_memoryVAPI returns: "Unknown tool: undefined"```
Same webhook works when tested directly (returns correct data)
Tool exists and is properly configured
Other 3 tools on same assistant work fine## QuestionWhy does VAPI return "Unknown tool: undefined" instead of calling the webhook? Is theresomething special needed for async tools on BYO numbers?Has anyone else experienced this with async tools?