The short answer
A virtual assistant (VA) is a person you pay to handle tasks, usually remotely and by the hour. An AI agent is software that works for you through a chat app, remembers how you like things done, and runs routine jobs on a schedule at any hour. Choose a VA for work that involves other people, phone calls or judgement calls. Choose an agent for repeating work like summaries, drafts and reminders. If you have both kinds of work, use both and split the tasks between them.
How a VA and an agent compare
| AI agent | Virtual assistant | |
|---|---|---|
| Availability | Any hour, on a schedule you set | Agreed hours |
| Cost model | Subscription plus model usage | Hourly rate or monthly retainer |
| Judgement | Follows your instructions and context | Weighs priorities, reads people |
| Contact with others | None: it drafts, you send | Calls, emails and chases on your behalf |
| Best at | Summaries, first drafts, reminders, reformatting | Scheduling with people, chasing, sensitive contact |
| Weak at | New situations, anything it hasn't been told | Volume, early mornings, weekends |
What can a VA do that an agent can't?
A good VA learns your business and starts making sensible calls on your behalf. They know that one client always pays late but is worth keeping, and that the council planning office answers the phone before 10.
They take loosely defined jobs. "Sort out the scaffolding company" is a task a person can run with. An agent needs it broken down into steps, and even then it can't ring anyone.
They deal with people. A VA can call a supplier, hear that something's wrong, and change approach mid-conversation. They can chase an invoice in a way that keeps the relationship intact.
They're accountable. When something goes wrong, a person can explain what happened, apologise to whoever was affected and put it right.
The limits are hours and cost. A VA works the time you've agreed, and covering early mornings, weekends or holidays costs more or doesn't happen.
What does an agent do better than a person?
An agent runs on a schedule. A briefing at 6:30 before your first site visit, a reminder on the last Thursday of the month, a draft report waiting when you open your laptop: it does these whether or not anyone's working.
It's consistent. The fiftieth weekly summary follows the same format as the first, and adding more of the same task doesn't mean more hours.
It remembers your context. A configured agent keeps your formats, preferences and corrections, so after a few weeks it knows your report template and your sign-off better than someone in their first month.
Its limit is judgement. When something happens that it hasn't been told about, it either asks or produces something plausible and wrong, which is why its work should reach you as drafts.
What does each one cost beyond the headline price?
For a VA, the rate is the visible part. Add the time you spend briefing and reviewing, which is heavy in the first month and never zero. Add recruitment, which often takes weeks, and the context you lose if they leave. A capable VA also tends to be given more work over time, which is good for you but makes the monthly cost harder to predict.
For an agent, the subscription is the visible part. Add setup: your documents, examples, formats and rules of thumb, usually days rather than minutes for anything beyond a simple task. Add review time, which shrinks as you build trust but doesn't vanish. And because an agent repeats what it's been told, a wrong instruction produces the same mistake every week until someone notices, where a person's slip is usually a one-off.
Counting both sides usually gives the same picture: the agent is cheaper per routine task, the person is better value for varied, relational work, and both cost more than their headline figure.
One practice, split between an agent and a VA
Priya runs a one-person structural engineering practice in Bristol. She spends most mornings on site and has a VA for ten hours a week. Before the agent, the VA's hours went mostly on admin Priya could have described in a checklist.
What the agent took over. A 6:30 briefing each weekday with the day's site visits, deadlines and anything overdue. Turning her typed site notes into a first draft of the inspection report in her standard format. A Friday list of unpaid invoices with a draft chaser for each. Reminders for professional indemnity renewal and CPD hours.
What stayed with the VA. Booking site visits with homeowners and builders, ringing the building control office, chasing the invoices that the polite email didn't move, and handling the client who was unhappy about a fee. Each of these needs a person's judgement about tone and timing.
What they do together. The agent drafts the invoice chasers; the VA checks them against what she knows about each client, adjusts two, and sends them. The agent drafts the report; Priya checks the engineering and signs it.
The VA's ten hours now go on work that needs a person, and Priya's evenings aren't spent writing reports from scratch.
Which should you choose?
A VA, if your work is varied and involves a lot of contact with other people, if you need someone to make calls or take loosely defined jobs, or if you only have a few hours a week to hand over.
An agent, if your work has tasks that repeat weekly or daily, you want things ready before working hours, or the same job happens often enough that a consistent format matters.
Both, if you have a steady flow of routine admin and enough people-facing work to justify a person. That's common once a business has more clients than the owner can keep in their head.
Neither yet, if you can't describe the work. Write down last week's tasks first; both a VA and an agent need that list to start.
When should you move work from the VA to the agent?
Start the agent on less than you think it can handle, with everything coming to you or your VA as a draft. When a task has run for a month and the drafts barely need editing, consider letting that one go through with lighter checking, provided a mistake would be cheap and easy to spot.
As routine work moves to the agent, give your VA the work that needs more judgement. Tell them why the role is changing, because a VA who thinks they're being replaced won't flag the agent's mistakes.
Move the line because of a month of real output, not because a demo impressed you.
Common questions
Is an AI agent cheaper than a virtual assistant?
Per routine task, usually yes. In total, only if you have enough repeating work to justify the setup. For a few hours a week of varied work, a person is often better value.
Can an agent replace a VA completely?
For narrow, repetitive work you can describe precisely, sometimes. For anything that involves calling people, negotiating or reading a situation, no, because an agent drafts but doesn't make contact on your behalf.
What should I hand to an agent first?
A task you do every week that has a clear format, such as a Monday plan or a Friday summary. Describe it in a sentence, give the agent an example of a good version, and have it send you drafts. Our list of everyday tasks for an agent has more ideas.
Can my VA work with my agent?
Yes, and it's often the best arrangement. The agent prepares drafts and summaries, and the VA checks, adds what only a person would know, and sends them.