Deliberate is whether the structure was chosen; deterministic is whether the output repeats. A toy is neither on the second try.
The sister word to deliberate, and the one people miss. Deliberate is about the structure: was this shape chosen, or did it just accumulate? Deterministic is about the behaviour: does the same input produce the same result on the second try, and the fiftieth, on an ordinary Tuesday when nobody's watching? One is a property of what you built; the other is a property of what it does. A system can be deliberate and still not deterministic — beautifully designed and quietly unrepeatable — which is exactly the trap AI walks people into.
The distinction is easiest to see through the toy and the instrument. A toy is deliberate enough — someone chose the prompt, framed the demo — but it isn't deterministic: it delights once and can't do it again, because nothing about the first success was reproducible. An instrument is both. It was shaped on purpose and it behaves the same way tomorrow, which is the only reason you can learn it, rely on it, and put real work through it. Reproducibility is what turns a good result into something you can build on.
The reason this matters more with AI than with ordinary software is that the model is the least deterministic part of the stack. Left alone it will answer the same question three different ways. Determinism doesn't come from the model getting better — it comes from the structure around it: fixed context it always reads, rules it must obey, and a validation loop that checks the output against something stable. The model stays probabilistic; the system becomes deterministic, because everything load-bearing lives outside the model.
So the two words are a matched pair, and the order runs one way. Deliberate is the cause; deterministic is the payoff. You choose the structure on purpose (deliberate) so that the output stops being a surprise (deterministic). Skip the first and the second never arrives — which is why "it worked in the demo" and "it works every Tuesday" are two entirely different claims, and only the second one is worth building a business on.