Async Webhook Tools with Live Conversation Injection for AI Assistants

23, Jan 2026

Synchronous webhook tools block assistant responses while waiting on external systems. This works for fast APIs, but breaks down when requests take longer than a few seconds. AI Assistants now support async webhook tools paired with live message injection, so long-running tasks can complete without interrupting the conversation.

What’s new

Async webhook request mode: Webhook tools can return immediately instead of blocking the conversation.
Parallel tool execution: Multiple webhook tools can run at the same time.
Call control ID propagation: Async requests include a call identifier in the request headers.
Live message injection: Tool results or system messages can be added to an active conversation.
Real-time context updates: Assistants incorporate new information as it arrives.

Why it matters

Prevents conversation stalls caused by slow or unpredictable backend APIs.
Avoids request timeouts during long-running operations.

Order status lookups that depend on external fulfillment systems.
CRM updates triggered during live support calls.
Data enrichment that runs alongside an active conversation.
Compliance or validation checks with variable response times.

In the Mission Control Portal, open your assistant and select a webhook tool.
Change the webhook Request mode from Sync to Async.
Ensure your backend reads the x-telnyx-call-control-id header.
Return a fast 200 response to acknowledge the webhook request.
Run the long operation asynchronously in your backend.
When results are ready, use the Add Messages API to inject a system message into the live conversation.

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Async Webhook Tools with Live Conversation Injection for AI Assistants

23, Jan 2026

What’s new

Why it matters

Example use cases

Getting started