A generic AI agent will ask generic questions and capture generic information. If your AI agent's first message to a new buyer lead sounds like it could come from any agency in any country, it won't inspire confidence — and buyers who aren't confident will click away.

Custom prompts change that. In Sift, your AI agent's behaviour is shaped by the system prompt you configure in your dashboard. Here's how to write one that actually works.

Start with your agency's voice

The system prompt opens with an identity instruction. This tells the AI who it is, what tone to use, and what agency it represents. Don't skip this section — it's the most important for getting the agent to sound like your team rather than a generic chatbot.

You are the virtual assistant for Marchmont Property, a boutique estate agency based in Edinburgh. You are professional, warm, and straightforward. You speak clearly and concisely — no jargon. You always refer to yourself as "the Marchmont team" rather than as an AI. When a buyer contacts you, your primary goal is to understand their situation, qualify their position, and if appropriate, book a viewing.

Notice what this does: it sets geographic context (Edinburgh), tone (professional, warm, concise), and a specific goal (qualify and book). The instruction to refer to "the Marchmont team" rather than "an AI" is optional but reduces the friction buyers feel when talking to an automated system.

Define your qualifying questions in UK terms

The most common mistake estate agents make when setting up an AI agent is leaving the qualification questions generic. Generic questions get generic answers. UK-specific questions get useful signals.

What to include:

Your qualifying questions should establish: 1. Chain status — ask "Are you currently in a property chain, or are you chain-free?" If they say chain-free, confirm by asking "So you don't have a property to sell before you can proceed?" 2. Mortgage readiness — ask "Have you received a mortgage agreement in principle (AIP) from a lender?" If they say yes, note it. If they're unsure what that means, explain briefly: "That's a written confirmation from a mortgage lender that they'd lend to you at a certain amount." 3. Cash buyer status — if they describe themselves as a cash buyer, ask "Are you able to proceed without selling another property first, or is your cash dependent on an upcoming sale or other event?" 4. Timeline — "When are you looking to move, ideally?" Record whether they say under 3 months, 3–6 months, or longer. 5. First-time buyer — "Is this your first property purchase?" This affects stamp duty and scheme eligibility.

These five questions, asked conversationally within the first four or five exchanges, give you enough to score any UK buyer accurately. The key is that they're conversational, not interrogative — the AI should weave them naturally into a dialogue, not fire them as a form.

Set your escalation rules

The AI agent should know when to hand off to a human. Set this explicitly in your prompt.

Escalate to a human team member (by flagging the conversation as "priority follow-up") when: - The buyer is chain-free with a DIP or cash buyer with immediate funds - The buyer wants to book a viewing for a property that requires agent presence - The buyer is asking questions you can't answer from the property information provided - The buyer expresses frustration or asks to speak to a person Do not promise specific viewing times you can't confirm — instead, say "I'll have a member of the Marchmont team confirm a time that works for you by [next business morning]."

This prevents the two most common failure modes: either the AI gets out of its depth and gives a wrong answer, or it creates a commitment the team can't fulfil.

Tune for your property type

If your agency specialises, use your prompt to focus the agent. A lettings agency prompt looks very different from a sales agency prompt.

Sales agency:

You are primarily helping buyers qualify for property purchases. Focus on purchase readiness: chain status, DIP, budget, and timeline to exchange. For off-market enquiries, collect basic information and note that a member of the team will contact them directly.

Lettings agency:

You are primarily helping prospective tenants enquire about rental properties. Establish: their required move-in date, number of occupants, monthly budget, whether they have pets, and whether they have a guarantor if required. Note that all applicants will need to complete a referencing check before tenancy can proceed.

Mixed sales and lettings:

At the start of every conversation, first establish whether the visitor is looking to buy, rent, sell, or let. Then follow the appropriate qualification path based on their answer.

Handle out-of-hours messaging explicitly

If your agent operates overnight — which it should, given that 40% of buyer enquiries arrive outside office hours (Moneypenny, 2025) — tell it what to do when someone books a viewing the team won't see until morning.

If a buyer wants to book a viewing and it is currently outside business hours (before 9am or after 6pm on weekdays, or on weekends), confirm their preferred day and time range, collect their contact details, and tell them: "I've noted your preferred time. A member of the team will confirm your viewing first thing [tomorrow / Monday] morning." Do not attempt to confirm specific appointment times without team input.

This avoids the awkward situation where a buyer wakes up Monday morning having "booked" a Tuesday viewing that no one in the agency knows about.

Test it before you go live

The best way to test your prompt is to role-play as three different buyer types:

  1. A hot lead — chain-free, DIP in hand, ready to view within three weeks. Check that the agent flags this quickly and offers to book.
  2. A soft lead — "just looking," no DIP, not sure when they'd move. Check that the agent handles this politely without over-promising.
  3. A lead with a question you didn't anticipate — ask about planning permission history, or leasehold length, or something highly specific. Check that the agent gracefully says it doesn't have that information and offers to have the team follow up.

If any of these three conversations produces an awkward or wrong response, adjust your prompt before pointing live traffic at the widget.

Keep it updated

Your prompt is a living document. When a property sells and you want the agent to stop discussing it, update your property listings. When your team's availability changes, update your escalation message. When you open a new branch, update the identity block.

The agents who get the most from Sift are the ones who treat the system prompt as part of their regular operations — not a one-time setup task.

For detailed documentation on system prompt configuration, see the Sift docs.