Custom AI Agent Development Services

We build and run AI agentsfor your business.

We build AI agents that answer every lead, send the quote, chase the invoice and write the Monday report, on the tools you already use. Completely managed by us, with new agents every month.

Book a 30-minute call See what agents do

A team you can text, email and call.

Each agent owns one job and gets its own email address and phone number. Text the quotes agent from your car. Forward a late invoice to the billing agent. Ask the chief of staff agent what slipped this week.

They work inside your tools. Anything that reaches a customer or touches money waits for a person to approve it, until the agent has earned more trust.

Example: an agent team for a 40-person services firm

  • Front desk

    frontdesk@yourco.com

    (555) 010-4410

  • Quotes

    quotes@yourco.com

    (555) 010-4411

  • Billing

    billing@yourco.com

    (555) 010-4412

  • Scheduling

    schedule@yourco.com

    (555) 010-4413

  • Reporting

    reports@yourco.com

    Slack: #numbers

  • Chief of staff

    cos@yourco.com

    (555) 010-4415

Quotes agent(555) 010-4411
  • You: Did the Henderson quote go out?
  • Quotes agent: Sent at 9:14. They’ve opened it twice. Want me to nudge them Thursday if they don’t reply?
  • You: Yes. Copy Dana.
  • Quotes agent: Will do. I’ll text you when they answer.
Example
Book a call to see one

You don’t need more software. You need the work done.

You already pay for a CRM, an inbox, a scheduler and an AI tool or two. The work still waits for someone to find the time.

  • New leads wait hours for a reply, and the company that answered first gets the job.
  • Quotes sit for days because one person knows the pricing.
  • Invoices age because nobody likes chasing money.
  • Someone loses Friday afternoon to the Monday report.
  • The AI tool you bought is still waiting for someone to set it up.

Building an agent is the easy part.

Keeping it working is the job.

Models update. Logins expire. Your prices change. A new kind of customer email shows up. Any one of those can quietly break an agent, and a handover doc won’t fix it.

So we stay.

We check every agent every day, fix what breaks the same week, tune it from your team’s edits, and add the next agent on your list each month.

AI agents for small and mid-sized businesses.

These are examples. Your first three come from a day watching how your team actually works.

  • Front desk agent

    Answers every call, text, chat and web form within a minute, day or night. Books the appointment or hands it to the right person.

  • Quotes agent

    Turns a call, an email or site-visit notes into a priced quote from your price list and past jobs. A person approves it before it goes out.

  • Follow-up agent

    Tracks every open quote, quiet lead and unanswered email, and drafts the nudge before anyone forgets.

  • Billing agent

    Sends invoices, matches payments and chases overdue accounts on schedule, politely, in your voice.

  • Scheduling agent

    Matches jobs to people on skills, location and availability, and handles the reschedules.

  • Inbox agent

    Sorts every inbound email and ticket, answers the repeat questions from your docs, and hands the rest to a person with a draft.

  • Onboarding agent

    Collects the forms, documents and logins a new client owes you, and chases whatever is missing.

  • Reporting agent

    Pulls the numbers from your tools every Monday and writes the summary an owner actually reads.

  • Chief of staff agent

    The one agent you text. It knows what every other agent did, what slipped and what needs you today.

Not sure which three to start with? We’ll pick them together on the call.

Book a 30-minute call

Working agents in two weeks. A bigger team every month.

  1. Week 1

    Watch the work

    We shadow your team for a day, map every repeat job, and pick the three agents that free the most hours.

  2. Week 2

    First agent live

    Built on your tools and real data. It drafts, a person approves, and we tune it from their edits.

  3. Weeks 3–4

    The team fills out

    The next two agents go live, each with its own inbox and phone number.

  4. Every month

    Run and grow

    We monitor and fix every agent, add one new agent, and send you a report on what they all did.

One monthly fee. One new agent every month.

Plans run from $5,000 to $15,000 a month, depending on how many agents you run and how many teams they serve.

  • Team

    From$5,000a month

    What’s included:

    • One department, up to 3 agents
    • Shadow day and setup
    • First agent live in 14 days
    • One new agent a month
    • Monthly report and review call

  • Department

    From$10,000a month

    Everything from Team plus:

    • Up to 8 agents
    • Two builds at a time
    • Weekly check-in
    • Fixes within one business day

  • Company

    From$15,000a month

    Everything from Department plus:

    • Agents across the company
    • First in the build queue
    • Security review support
    • Your team trained to build its own

Setup is quoted on the first call. Three-month minimum, then month to month. You own everything from day one.

Every plan starts with a 30-minute call.

Book the call

Guardrails from day one.

  • Every agent starts in approval mode: it drafts, a person sends.
  • Money, contracts and anything legal always get a human check.
  • Each agent only reaches the tools its job needs.
  • A log of every action, so you can see what it did and why.

Built, trained and coached.

Custom Agents

How Go Nimbly became an AI‑first agency.

“For the last ten years, we’ve been committed to becoming a tech‑enabled agency. In the last six months, we’ve made more progress toward that than we did in the first ten.”

Jen IgartuaCofounder & CEO, Go Nimbly
Read the case study
1:1 AI Coaching

250%+

paid conversion increase

“I thought I was an AI power user… until Mark made me realize I had no idea what was actually possible.”
Angel OlavarriaCEO, Strive Skin
Read the case study
Executive AI Workshop

80%

of employees use AI every week

“Mark really helped us develop the framework. Once we had that, I felt comfortable with our executive team leaning in. This led to 40% revenue growth.”
Michael BoordPresident & COO, ServiceCore
Read the case study

Read every case study and review

In their words.

“Mark built us an amazing application that our team uses daily. Made our lives so much easier!”

Dan Guidebeck

Custom application client

“Mark built a custom platform for our team and it’s been a game changer for visibility into our day-to-day and automating more of our project management.”

Emily McGrath

Custom platform client

“This is going to be our operating system for the practice.”

Engagement Manager

100-person RevOps consultancy

“The AI Operating System really calls me out, which is fantastic. Now the whole team shares one definition of what “done” means.”

RevOps Architect

100-person RevOps consultancy

5.0 rating on GoogleRead all reviews and case studies

Mark Fershteyn

Who builds and runs it.

Me, Mark Fershteyn. 15 years in B2B sales and GTM, including 7 years founding and running Recapped, a B2B sales software company that raised $8M. I build with Claude Code, 1,500+ hours so far. I take on a few agent teams at a time, so the person who built yours is the one who answers when something breaks.

Book a call with me

Good fit

  • 10 to 1,000 people
  • A job your team does 20+ times a week that follows rules
  • A CRM, inbox and calendar your team actually uses
  • A leader who’ll review the agents’ work 30 minutes a week

Not a fit

  • You want a website chatbot
  • You want agents with no one on your team approving their work
  • You run a RevOps or GTM consultancy (we have a conflict there)

Sound like your company?

Book a 30-minute call

Pricing, timelines and ownership.

Our managed agent teams run from $5,000 to $15,000 a month, plus a one-time setup fee. The price depends on how many agents you run and how many teams they serve. It covers the build, running and fixing every agent, and one new agent a month. You get a written price after the first call.

An agent we build and then keep running for you. We check it every day, fix it when a tool or model changes, improve it from your team’s edits, and add new agents as you find more work to hand off. You pay monthly and own everything we build.

Yes. A one-time build fits if someone on your team can fix the agent when a login expires, a model changes or your process moves. Most small and mid-sized companies don’t have that person. With a managed team, we are that person.

Your first agent is live on your real data within two weeks of kickoff. The next two follow in weeks three and four. After that, we add one new agent a month.

Your first agent is doing the job we agreed on, on your real data, within 14 days of kickoff. If it isn’t, month one is free.

The ones that pay off first are the boring jobs: answering every lead, sending quotes, chasing invoices, booking and rescheduling, sorting the inbox and writing the weekly report. If someone does it 20 or more times a week and it follows rules, an agent can probably take it.

Yes. The agents, prompts, code and accounts are yours from day one and run under your logins.

Cancel after month three with 30 days’ notice. You keep every agent, prompt and account, plus a runbook to keep them running.

When the job needs one, yes. Your front desk agent can answer calls and texts, and your billing agent can send from billing@yourcompany.com. Your team reaches every agent the way it reaches a coworker.

It will, so we plan for it. Every agent starts by drafting for a person to approve, and money or legal risk always gets a human check. We tune each agent from your team’s edits and only loosen approval once its work stops needing them.

We’re an AI agent development company that also runs what it builds. Mark Fershteyn builds every agent team himself and takes on a few at a time, so whoever built your agents is who fixes them.

For prospecting, outreach, follow-up and content agents, see GTM engineering. This page covers the rest of the business: the front office, the back office and operations.
GTM EngineeringAI Transformation PlaybookAI ImplementationManaged AI EmployeesAI ConsultingAll solutions

What will you hand off first?

Book 30 minutes. I’ll show you a working agent team, then we’ll pick the first three for yours.

Book a call with Mark

Sales and marketing agents for B2B teams have their own page.

See GTM engineering