how to build an AI agent for lead follow-up (step by step)

responding to leads within 5 minutes makes you 21x more likely to close. most companies take 42 hours. here's how to build an AI agent that responds in under 60 seconds.

Feb 16, 2026

78% of customers buy from the first company that responds. the average business takes 42 hours to respond. most leads are never contacted at all.

that's not a sales problem. it's a systems problem.

contacting a lead within 5 minutes makes you 21x more likely to qualify them compared to waiting 30 minutes. responding within one minute increases conversion by 391%. every minute after that, the probability of making contact drops.

we build AI agents that respond to leads in under 60 seconds. here's the architecture, the logic, and the implementation path for any service business doing $1M-$50M in revenue.

what the agent does

the lead follow-up agent handles the first 3-5 minutes of every new lead interaction. that's the window where the prospect is most engaged, most available, and most likely to convert.

the agent:

  • triggers instantly when a lead enters your system (form fill, phone call, ad click, email inquiry)

  • sends a personalized text and email within 60 seconds

  • asks 2-3 qualifying questions based on the lead source

  • collects contact information and key details

  • scores the lead based on responses and behavior

  • books a call or meeting with the right rep

  • logs everything in your CRM

it doesn't replace your sales team. it fills the gap between "lead submitted" and "rep available." that gap is where most deals die.

the math behind speed to lead

the data is consistent across every study.

forbes and InsideSales.com: leads are 100x more likely to qualify if contacted within 5 minutes versus 30 minutes.

velocify: responding within one minute yields 391% higher conversions compared to waiting even two minutes.

harvard business review: companies are 7x more likely to qualify a lead when they respond within the first hour.

and the reality check: 57% of companies take over a week to respond. 51% of leads are never contacted.

this isn't about having better salespeople. it's about having a system that responds before your team is even aware a lead came in. AI agents solve this because they work 24/7, respond in seconds, and never forget to follow up.

the architecture

there are four components. each one is straightforward.

1. trigger layer

every lead source connects to a single intake point. web forms, facebook ads, google ads, phone calls (via voicemail transcription or missed call detection), email inquiries, chat widgets. each one fires a webhook or API call when a new lead enters.

tools: zapier, make, or direct API integrations. the trigger needs to fire in under 10 seconds. if your CRM takes 5 minutes to process a new contact, you've already lost the window.

2. AI response layer

the agent receives the lead data (name, email, phone, source, any form fields) and generates a personalized response. this isn't a template. it references the specific action the lead took, the service they inquired about, and a relevant question.

example: someone fills out a form for commercial insurance on your website. the agent sends a text: "hey [name], got your quote request for commercial coverage. two quick questions so we match you with the right producer. what's your current renewal date? and what type of business are you covering?" this goes out in under 60 seconds.

tools: claude API or GPT-4 for message generation. twilio for SMS. sendgrid or your CRM's email API for email. the AI generates the message. the delivery tools send it.

3. qualification layer

the agent runs a conversation, not a monologue. when the lead responds, it processes their answers, asks follow-up questions, and scores them against your qualification criteria.

for a service business, qualification typically covers: budget range or revenue size, timeline or urgency, decision-making authority, and specific needs. the agent collects this through 2-4 natural text exchanges.

leads that score above threshold get routed to a rep with a full briefing. leads that score below get added to a nurture sequence. no manual sorting required.

4. handoff layer

when a lead is qualified, the agent books a meeting directly on the rep's calendar. it sends the rep a summary: lead source, qualification answers, sentiment, and recommended next steps.

the rep walks into the call already knowing what the prospect needs, what they said, and why they're a fit. no cold start. no "so, what brought you to our website?"

tools: calendly or cal.com for scheduling. CRM integration for logging. slack notification for the rep.

what this costs to build

for a mid-market service business, the build breaks down like this:

basic version (form + text + email + CRM logging): $3K-$8K flat fee. handles one lead source. responds via text and email. logs to CRM. books meetings. 2-3 weeks to build and deploy.

full version (multi-source + qualification + routing + nurture): $8K-$15K. handles all lead sources. runs full qualification conversations. routes to the right rep based on territory, service type, or availability. drops unqualified leads into automated nurture. 4-6 weeks.

ongoing costs: twilio (SMS) runs about $0.0079 per message. AI API calls (claude or GPT) run $0.01-$0.10 per interaction depending on model. for 500 leads per month, you're looking at $50-$100/month in variable costs.

compare that to a missed deal. if your average client is worth $5K-$50K per year in revenue, missing one qualified lead per week costs you $260K-$2.6M annually. the agent pays for itself the first time it catches a lead your team would have missed.

results from our builds

we build these agents for clients across insurance, real estate, construction, and professional services.

one construction client went from 4-hour average lead response to 2 minutes. conversion doubled. the agent handles after-hours leads that used to wait until the next business day.

a commercial real estate client cut outreach time by 18 hours per week. revenue increased 25% in four months. the agent qualifies leads and schedules showings without a human touching the process until the meeting itself.

companies using AI-based lead scoring report 30% higher conversion rates and cut follow-up time by 60%. that matches what we see across deployments.

how to start this week

you don't need to build the full system on day one. start with the highest-impact piece.

week 1: connect your highest-volume lead source (usually web forms or ad leads) to an AI agent that sends a text within 60 seconds. just the text. no qualification. no routing. measure the response rate against your current baseline.

week 2-3: add qualification questions. start logging responses. route qualified leads to your best closer.

week 4-6: expand to additional lead sources. add email follow-up sequences. implement lead scoring. connect to CRM.

the first version takes days, not months. the ROI shows up immediately because you're fixing the biggest leak in your funnel: the gap between lead submission and first contact.

35-50% of sales go to the first responder. the agent makes sure that's you. every time.

we build lead follow-up agents for service businesses every week. flat fee. working system. deployed in 2-3 weeks.

book a call → agentintegrator.io