Short answer: to choose a reliable B2B prospecting agency, check five signals before signing: a claimed reply rate consistent with the market (7 to 11% average, up to 30-60% for the best offers and sectors), transparency about who actually writes the messages, respect for LinkedIn limits (roughly 28 invitations per day), a contract without a forced long-term commitment, and a real trial period.
More and more consultants and SMBs are also comparing that price against an autonomous AI agent, which does the same work from €97 per month.
A B2B prospecting agency sells a simple promise: fill your calendar without you having to prospect yourself. The problem is that promise hides very different realities depending on the provider.
Some agencies have real expertise. Others resell a generic template at a high price. Here is how to tell the difference before you sign a multi-month contract.
Why do so many prospecting agencies disappoint?
Because B2B prospecting is a specific craft, one few salespeople actually master, and the word "agency" guarantees no particular method.
The most common symptom: a consultant or SMB signs for a volume of sends, not for a result. Prospect qualification, real message personalization, and reply handling stay vague in the contract.
The result: generic messages sent at scale, a reply rate close to the standard market average (7 to 11%), and a high monthly bill for a volume you could have produced yourself with a good tool.
What signals should you check before signing with an agency?
Five questions to ask before any commitment, in the order they matter most.
- Who actually writes the messages? A junior applying a template, or a system that personalizes from real signals on each prospect (a recent post, a mutual connection, company news)?
- What reply rate is claimed, and on what basis? A number with no calculation method or verifiable sample is a marketing figure, not data.
- Does the volume respect LinkedIn's limits? The platform caps everyone at roughly 28 invitations per day, a limit documented on LinkedIn's official help page. An agency promising several hundred invitations a week is risking your account, not theirs.
- Does the contract force a long commitment with no exit? A 12-month commitment with no exit clause before you've seen a single result is a red flag.
- Is there a real trial period? Two to four weeks is usually enough to see the first replies land and judge on evidence.
If an agency cannot answer these five questions clearly, the price on the table has no comparison value.
"What an agency sells you is human time. What you should be buying is a mechanism: who targets, who writes, who follows up, and at what pace," says Laura Terriou, founder of Formula.
Human agency or AI prospecting agent: how do they compare?
Both options serve the same function, but through very different mechanisms. Here is the factual comparison.
| Criteria | Classic prospecting agency | AI agent (Formula.) |
|---|---|---|
| Who writes the messages | One or more human prospectors, often junior | The agent, from real signals on each prospect |
| Channels | Varies by contract, often LinkedIn only | LinkedIn + email in parallel on the same prospects |
| LinkedIn limits | Depends on the provider's rigor | 28/day enforced by default |
| Reply validation | Forwarded by email or report, variable delay | Mobile swipe, reply in under 5 minutes |
| Indicative price | $1,500 to $5,000/month | From €97/month, 2-week trial |
| Commitment | Often 6 to 12 months | No forced long-term commitment |
The full breakdown on what a human and an AI each do well in this context is in Human SDR or AI Prospecting Agent for B2B.
A real case: why switch from an agency to an AI agent
Sarah runs a consulting firm. Before Formula., she worked with a classic prospecting agency, with a part-time dedicated prospector.
The monthly price was high for a volume limited by one person's availability, and the messages stayed generic despite promises of personalization.
After switching to an AI agent that prospects continuously on LinkedIn and email with the same qualified prospects, her firm went from $20,000 to $55,000 in monthly revenue, while cutting the time spent managing prospecting.
The mechanism behind the gap: a steady volume of 840 qualified prospects per month, and a measured reply rate between 30 and 60% depending on the offer, versus 7 to 11% market average.
On Formula.'s own account, 283 first messages generated 114 replies, a 40% reply rate (data from July 23, 2026). See the full case study.
How much should a B2B prospecting agency cost in 2026?
A B2B prospecting agency most often costs between $1,500 and $5,000 per month for a part-time dedicated consultant, more depending on volume and channels covered.
That price mostly reflects billed human time, not necessarily a guaranteed result. The full profitability breakdown is in what a qualified meeting actually costs in 2026.
And human time dilutes fast: according to Salesforce, sales reps spend less than 30% of their time actually selling (Salesforce). Agencies are not exempt from that mechanic.
An autonomous AI agent covering a comparable scope starts at €97 per month, with a 2-week trial to judge on concrete results before any commitment.
The agent prospects. You collect meetings in your calendar.
Want to compare it directly on your business, with real numbers?
Start the 2-week trialFirst replies usually land within the trial. Judge on evidence, not promises.
Frequently asked questions about choosing a B2B prospecting agency
How do you know if a B2B prospecting agency is reliable?
Check five signals before signing: a claimed reply rate consistent with the market, transparency about who writes the messages, respect for LinkedIn limits, a contract without a forced long-term commitment, and a real trial before you commit.
What reply rate is normal for a serious prospecting agency?
The market average sits between 7 and 11% on classic B2B outreach. An agency or agent that genuinely personalizes each message can reach 30 to 60% depending on sector and offer.
Be wary of a much higher promised rate with no proof.
Should you choose a human agency or an AI prospecting agent?
A human agency bills prospector time, with a high monthly cost and limited capacity. An AI agent prospects continuously on LinkedIn and email and has you validate replies with a swipe.
The choice mostly comes down to budget and how much control you want to keep.
How much does a B2B prospecting agency cost in 2026?
Most often between $1,500 and $5,000 per month for a part-time dedicated consultant. An autonomous AI agent like Formula. starts at €97 per month for a comparable scope.
What red flags should you watch for before signing with an agency?
A promised volume far above the LinkedIn limit of 28 invitations per day, no verifiable client cases, a 12-month contract with no trial period, and vagueness about who actually writes the messages.