Give your agent tools: check slots, look up orders and create leads mid-call
An agent that can only talk is a phone menu with better manners. Tools let it look things up and get things done while the caller is on the line.
The Vaakyo team2 min read
- Tools
- Integrations
- Engineering
Without tools, a voice agent can only answer from its prompt and knowledge base. With tools, it can check a doctor's real availability, find an order by its number, create a lead in your CRM or book a slot, all while the caller waits a second or two.
What a tool is
A tool is an HTTP endpoint on your side that the agent calls with arguments it collects from the conversation. You describe it to the agent with a name, a description and the parameters it takes:
| Name | Description | Parameters |
|---|---|---|
find_order |
Look up an order by its number or the caller's phone | order_id (optional), phone |
check_availability |
Open appointment slots for a doctor on a date | doctor, date |
create_lead |
Save a qualified lead to the CRM | name, budget, timeline |
The agent decides when to call a tool from the conversation and your descriptions, so write descriptions the way you'd explain the tool to a new colleague.
Design tools for a phone call
- Return little, return it fast. The agent has to turn the result into one or two sentences. Return the three slots it should offer, not a calendar of the month. Aim for responses well under a second.
- Return text the agent can say. "Tuesday 11:30 AM with Dr. Mehra" is easier to speak than an ISO timestamp.
- Make errors explicit. Return
{"found": false, "reason": "no order with that number"}rather than a 500, so the agent can say something useful. - Make writes idempotent. If a call drops and the caller calls back, booking twice should not create two appointments. Accept a key such as the call id.
Say something while you wait
For anything that might take more than a moment, have the agent say a short filler ("Ek second, main check karti hoon") before the tool runs. Silence on a phone line reads as a dropped call.
Security
- Tools must be on the public internet over HTTPS; never expose internal admin APIs to an agent.
- Authenticate the agent's requests to your endpoint (a secret header) and validate every argument: they come from a conversation, so treat them as user input.
- Give each tool the narrowest permission it needs. A tool that books appointments should not be able to delete them.
Test them before callers do
Use the tool tester in the console to send sample arguments and check the response, then talk to the agent and watch the call timeline: it shows each tool call, its arguments, the result and how long it took.
