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Build an agent
Agents
An agent is a prompt, a voice, and a set of capabilities — tools, a knowledge base, appointment booking, transfer — that every call routed to it shares.
Core fields
namestringrequiredInternal label. Callers never hear it.
systemPromptstringrequiredWho the agent is and how it behaves. Everything else in this page layers on top of it.
openingMessagestringrequiredThe first thing said on the call. Runs through merge fields (below) before it's spoken.
languagestringen, or a language code (es, fr, hi, ...), or multi to reply in whatever language the caller used last.
interruptSensitivity'patient' | 'balanced' | 'snappy'How readily the caller can talk over the agent mid-sentence.
voiceEngine'classic' | 'deepgram_agent' | 'sarvam'Which speech/LLM pipeline runs the call — see Voice engines.
Merge fields
The opening message — and the system prompt — can reference the lead being called with {{name}}, {{phone}}, {{email}}, or any custom field a lead carries, e.g. {{plan}} for a field named plan. A tag with no matching value on that lead is stripped rather than spoken literally — a greeting reading thanks for calling, {{company}} is delivered as “thanks for calling,” rather than the raw tag, so it’s worth testing a template against a lead that’s actually missing the field.
Appointment booking
Turning on appointmentBookingEnabled gives the agent four built-in capabilities it can use mid-call without any tool configuration: listing a caller’s existing appointments, checking available slots, booking one, and cancelling one. It reads and writes the same Appointment records the dashboard’s Appointments page shows.
Handing over to a person
Set a transferNumber and the agent can move a live call to it — the caller asking for a human, sounding upset, or the conversation going somewhere outside what the prompt covers. It always says a short handover line first; the call moves only once that line has finished playing, never in silence.
What else an agent can carry
- Tools — HTTP calls before, during or after a call. See Tools.
- A knowledge base — reference material it can search mid-call. See Knowledge base.
- A phone number —
outboundPhoneNumber, which also decides which agent an inbound call to that number reaches.