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A tool is an action the agent can run during the call: query an API, book an appointment, transfer, hang up, or send a WhatsApp.
📷 Screenshot needed — the tool builder, showing the available types.Save to /images/en/voice-agents/tools-builder.png

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How they work

Tools are an account-wide library, not per agent. You create one once under Voice → Tools, then attach it to whichever agents need it. The same tool can serve many agents.
1

Create it

Under Voice → Tools, pick the type and configure it.
2

Attach it

In the agent editor, the Tools button → add.
3

Map the parameters

Connect each of the tool’s parameters to a variable in your prompt.
The type can’t be changed after the tool is created. If you pick wrong, you have to create another.

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The description is the trigger

It’s the most important field and the most underestimated: the AI decides when to use a tool by reading its description.
Don’t describe what the tool does, describe when it should be used.Weak: Checks order status. Strong: Use when the customer asks about an order and has given an order number. Do not use if they're only asking about shipping times in general.

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The seven types

Method, URL, parameters, headers and body. Responses are mapped with JSON paths (customer.id, data[0].name) and those values become output variables.Any {{token}} you write in the URL, parameters or headers becomes an input variable for the AI to fill.Advanced options: timeout (120 s by default), a message while it runs, and a message after it finishes (on by default).
The request is always sent as application/json, even if you set another header.
Destination in E.164 format (+[country][number]), with an optional extension.Two modes:
  • Cold Transfer — direct handoff, the agent drops out.
  • Warm Transfer — the agent introduces the caller and waits for a human to pick up. Supports hold music, a private message for whoever answers, and a public one for the caller.
One field that matters: the trigger prompt, describing when the conversation should end. Optionally, a message right before hanging up.
Keep the trigger narrow. Ending too eagerly cuts customers off mid-thought — “customer confirms it’s resolved” works better than “conversation seems done”.
This tool’s helper text is worded for chat (“before the chat ends”) because the component is shared with WhatsApp and SMS. On a call it means hanging up.
Passes the call to another voice agent, which continues the same conversation rather than starting fresh. You can choose which agents the post-call analysis is attributed to.
Against Dialtu’s native calendar. Eight operations, split between reads and writes:Reads: list services, list professionals, list appointment types, check availability, list the customer’s appointments. Writes: book, reschedule and cancel an appointment.Settings: times to offer (1–20, default 5), days to look ahead (1–30, default 7), and whether it sends a confirmation message.
Booking and rescheduling only work well if the agent can also check availability. Enable the reads alongside the writes — nothing forces you to, but without them the agent books blind.
Today there is one provider available: AgendaPro, with ten operations (six reads and four that modify real data).
There’s no screen for you to connect integrations yourself. The Dialtu team makes the connection. In the builder you’ll only see a status indicator — if it says Not connected, ask your Dialtu contact to link it before going live.
On a call the agent reads results aloud, so keep the set of operations small: every extra capability is one more thing it may reach for mid-conversation.
A voice agent can send an approved WhatsApp template during the call — useful for sending a link, a confirmation or a location while talking.Each template variable is filled either from server context (automatic, never shown to the AI) or as an AI argument.
Use server context for anything the model shouldn’t invent.

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Attaching and mapping

The editor’s Tools button opens the list of attached tools. Selecting one lets you map each parameter to a prompt variable. Two behaviours worth knowing:
Removing a tool cleans its variables out of the prompt automatically — the words stay, but the {{ }} braces go.
Renaming a variable on the tool rewrites the prompt in place.
In the attached-tools panel, Calendar, Integration and WhatsApp Template tools all display an API label. It’s a known display bug: the tool works correctly, it’s just mislabelled.

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Next step

Test and activate

Test the agent before leaving it to handle calls.