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The prompt is your agent’s operating script: who it is, what it knows, how it runs the call, and what it must never do — written in plain language, in any language. This page covers how to structure one, the tactics that matter most on a phone call, and three complete templates to start from.
Migrating from another platform? Paste your existing prompt — or your whole exported agent JSON — into the copilot and ask it to set the agent up for you.

Start from a skeleton

Almost every good voice-agent prompt answers five questions. Use the section headings — they cost nothing and keep long prompts editable:
The builder’s prompt editor shows estimated tokens as you type and flags common problems — an empty prompt, leftover template placeholders, or a missing escalation path. The first 5,000 estimated tokens are included in the base rate; longer prompts use block-based surcharge pricing.

Tactics that matter on a phone call

Specific beats general

Vague instructions produce vague agents. Name the exact behavior you want:

Write for the ear, not the eye

Callers hear the agent — they can’t skim or re-read. Tell the agent to keep spoken turns short, ask one question at a time, and say how to read data aloud:

Confirm anything you’d hate to get wrong

Speech recognition mishears names, digits, and addresses. Build read-back into the flow:

Script the unhappy paths

The happy path writes itself; calls are won and lost everywhere else. Give the agent a line for each situation you can foresee — the wrong number, the furious caller, the question you can’t answer:

Always give the call somewhere to go

Every agent needs a hand-off path — a transfer number, a callback promise, or both. The prompt editor warns when it can’t find one.

Call actions are plain prompt lines

Transfers, keypad presses, hold, and hang-ups need no separate configuration — describe them where they belong in the flow:

Facts belong in knowledge, behavior in the prompt

Don’t paste your website into the prompt. Attach a knowledge base and the agent searches it mid-call — the prompt stays short, and updating a policy doesn’t mean re-editing the script. Keep the prompt for identity, flow, and rules; push catalogs, FAQs, and long policy text into knowledge.

Personalize per call with dynamic config, not placeholders

Prompts have no template-variable system — a leftover {{customer_name}} from another platform will be read as literal text, and the builder flags it as an unresolved placeholder. To vary the prompt per caller (VIP routing, logged-in user context), rewrite it at call time with dynamic call config.

Write in the language you want to hear

The prompt can be written in any language, and the agent follows it. Which language the agent speaks is set separately — the primary language starts the call, and any additional languages switch automatically when the caller uses one.

Templates

Three complete prompts to copy, then make yours: swap in your business facts, numbers, and policies.

Front-desk receptionist (inbound)

Order support with a lookup tool (inbound)

Attach an API connection or connected app for the order lookup, and a knowledge base holding the returns policy.

Appointment reminder (outbound)

For outbound scripts, also set who speaks first and voicemail handling in advanced call behavior — the prompt covers the conversation, the settings cover the pickup.
Outbound calling has legal requirements — consent, calling hours, and identification rules vary by region. Review the outbound calling laws guide before running campaigns.

Iterate until it survives real callers

No prompt is right on the first draft. The loop that works:
  1. Talk to it. Click Talk in the builder and probe the edges yourself — interrupt it, go off script, mumble a phone number. This is the fastest tweak-and-retry loop.
  2. Simulate calls. An AI caller runs whole conversations against your agent, scenario by scenario.
  3. Build a validation set. Turn the scenarios you care about into a repeatable suite you rerun after every prompt change.
  4. Split-test in production. When two phrasings both seem fine, let real calls decide.
Every deploy is snapshotted in the History tab, so prompt changes are safe to ship often — you can always inspect the diff and roll back.

Next steps

Build your first agent

The builder end-to-end: prompt, engine, voice, tools, deploy.

Knowledge bases

Give the agent facts to search instead of a longer prompt.

Dynamic call config

Rewrite the prompt per call from your own backend.

Every agent setting

Supervision, who speaks first, voicemail, silence check-ins, and more.