### Answer The inbound webhook notifies your server when an inbound call or SMS is received, allowing you to process it before the call connects. [(1) ]() ## How It Works When an inbound call/SMS comes in, Retell sends a

POST

request to your configured endpoint with the event payload. The webhook has a 10-second timeout and will retry up to 3 times if no 2xx response is received. ### Request Payload Example

json
{
  "event": "call_inbound",
  "call_inbound": {
    "agent_id": "agent_12345",
    "agent_version": 1,
    "from_number": "+12137771234",
    "to_number": "+12137771235"
  }
}

Note: The call/SMS is not yet connected at this point, so no call object or call ID exists in the payload. ### Response Options Your response can include (all optional) : -

override_agent_id

– use a different agent -

override_agent_version

– use a specific agent version -

dynamic_variables

– set call-specific variables -

metadata

– attach custom metadata -

agent_override

– override agent settings for this call only ### Common Use Cases - Filter and reject unwanted inbound calls/SMS - Add context (dynamic variables, metadata) to calls - Override agent ID or settings per call - Internal system records of inbound activity ### What Happens If the Webhook Fails? If all retry attempts fail, Retell checks if the number has an inbound agent ID set—if so, it connects to that agent; otherwise, it disconnects the call.

​ To learn more, see the sources I considered: [[1] Inbound webhook](https://docs.retellai.com/features/inbound-call-webhook) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer You can see the dynamic variables set via the inbound webhook in the call object after the call. The

retell_llm_dynamic_variables

field contains the dynamic variables that were passed at the start of the conversation. [(1) ]() When you retrieve call details using the List Calls API, the response includes:

javascript
"retell_llm_dynamic_variables": {
  "customer_name": "John Doe"
}

Additionally, there's a

collected_dynamic_variables

field that shows dynamic variables collected during the call, available after the call ends.

javascript
"collected_dynamic_variables": {
  "last_node_name": "Test node"
}

You can also see these variables in the

call_started

webhook event, which includes the dynamic variables passed using the inbound webhook. [(2) ]()

​ To learn more, see the sources I considered: [[1] List Calls](https://docs.retellai.com/api-references/list-calls) [[2] Personalization with Airtable]() ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer You don't need to do anything special in the prompt first, but there are a couple of things to check: 1. Response Format – Your webhook response must include the

dynamic_variables

field nested under `call_inbound`: [(1) ]()

json
{
  "call_inbound": {
    "dynamic_variables": {
      "first_name": "John",
      "email": "john@example.com"
    }
  }
}

2. All Values Must Be Strings – A common issue is passing non-string values. For example, passing

false

(boolean) instead of

"false"

(string) will cause variables not to be passed to the call. [(2) ]() , [(3) ]() 3. Reference Variables in Your Prompt – To use the variables in your agent, reference them with double curly braces like

{{first_name}}

or

{{email}}

in your prompts, begin message, or tool configurations. , [(4) ]() 4. Check the Webhook URL Location – Make sure your inbound webhook URL is set at the phone number level (via the

inbound_webhook_url

field on the phone number configuration) . [(5) ]() , [(6) ]() If variables still aren't appearing, verify your webhook is actually being called and returning a 2xx status with the correct JSON structure.

​ To learn more, see the sources I considered: [[1] Inbound webhook](https://docs.retellai.com/features/inbound-call-webhook) [[2] Dynamic Variables From Inbound Webhook Not Passed to the Call](https://discord.com/channels/1186424376300679209/1419725903918923920) [[3] Dynamic Variables](https://docs.retellai.com/build/dynamic-variables) [[4] Discord message from @danishkhan18 on 2025-01-27](https://discord.com/channels/1186424376300679209/1186462578310910112/1333229197002543127) [[5] Get Phone Number](https://docs.retellai.com/api-references/get-phone-number) [[6] Inbound Calls Webhook Issue](https://discord.com/channels/1186424376300679209/1420797324535533740) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

Thanks for the follow-up, @K Rudy. I'll get back to you soon.

​ To learn more, see the sources I considered: [[1] Dynamic Variables](https://docs.retellai.com/build/dynamic-variables) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.