An AI vendor demo, the kind that lands a contract, is a piece of theatre. That is not a criticism. The vendor's job is to land the contract, and a polished demo is one of the legitimate tools for doing that. The buyer's job is different. The buyer has to figure out whether the thing being demoed will hold up against the buyer's actual data, the buyer's actual workflows, and the buyer's actual edge cases. A polished demo, run on the vendor's own examples, does not tell you that.
Here is what a useful demo looks like, and what a buyer should ask for before agreeing to sit through one.
Run on your data, not theirs
The single most useful change a buyer can request is that the demo runs on the buyer's own data. Pick a dozen real examples from the workflow the tool is meant to handle. Hand them to the vendor a week in advance. Watch the demo on those examples.
Vendors will sometimes resist this, and the resistance itself is informative. A vendor who cannot demo on a dozen of your real documents inside a week is telling you something about how brittle the underlying system is, or about how much manual setup the production version will need.
Show me what it gets wrong
A demo that shows only the happy path is a sales document, not a technical one. Ask the vendor to walk through a case the system handles badly. Every AI system has them. The interesting question is whether the vendor knows where their failure modes are, and whether they will be candid about them on a call.
If the vendor cannot produce a failure case on request, the most likely explanation is that they have not stress-tested the system on data that looks like yours. The next most likely explanation is that they have, and they would prefer you did not see what came back.
Three questions vendors will dodge
There are three questions that come up repeatedly in vendor demos and that vendors tend to deflect. Worth asking all three, and worth noticing the texture of the answer.
First: what is the model under the hood, and what happens to your data when it passes through. Second: when the model returns something wrong, how does the customer find out, and how quickly. Third: what does the support relationship actually look like 12 months in, after the implementation team has rotated off.
None of these questions are unfair. A vendor with confidence in the answer will answer plainly. A vendor without confidence will redirect to the value proposition, the roadmap, or the case studies. That redirection is itself an answer.
Let the audience interrupt
A demo where the audience cannot interrupt the flow is a presentation, not a demonstration. Insist on the right to stop the demo at any point and ask the operator to try a different example, change an input, or rerun the same case with one variable changed. The vendor's comfort with being interrupted maps closely onto the depth of their actual product.
The case for an independent demo
There is a reasonable argument for paying someone independent to run a demo for you, instead of relying on the vendor's. The independent operator has no interest in the contract closing. They will use your data without negotiation. They will surface failure modes by default rather than on request. They will tell you, in writing, whether the system would solve the problem you actually have.
It costs money to do this, and that cost is real. But on a contract worth six or seven figures across its lifetime, the cost of an independent half-day demo is small enough that the only reason not to do it is institutional inertia. The clearer the eventual decision, the smaller that cost looks in retrospect.