What we look at
None of the form fields are decoration. Each one shifts the advice in a specific direction.
The bean
Origin and process change how the bean extracts. Washed Ethiopians are bright and unforgiving. Naturals are fruitier with wider tolerance. Anaerobics can swing from sweet to funky on a 1°C temperature change.
Roast level sets the temperature window. Light roasts want 94 to 96°C and longer pulls (35 to 45s) to coax sweetness out. Medium-dark wants 88 to 92°C and 22 to 28s before tipping into ashy.
Days off roast matters more than people think. Under 5 days your shot will gush and bloom inconsistently from outgassing CO2. Past 60 days the bean is stale and no amount of dialling in fixes that. The sweet spot is roughly 10 to 21 days.
The machine
Every machine has known behavioural quirks the community has documented. The Gaggia Classic Pro swings ±10°C between cycles and needs temp surfing. The Bambino ships with a dual-wall pressurised basket by default that invalidates every dial-in variable, so we'll ask if you haven't mentioned which basket you're using. The Lelit Bianca has a paddle for low-pressure pre-infusion that helps light roasts. The Linea Mini has commercial-grade temp stability, so problems are almost certainly bean or grinder.
We bake these specifics into the advice. Telling a Gaggia owner to "raise the temp" without acknowledging they can't control it precisely would be useless.
The grinder
The single biggest variable in espresso, and the one most people under-invest in. The knowledge base knows the Niche Zero's low retention and wide distribution, the DF64's popcorning and burr-alignment lottery, the Mazzer's commercial-grade retention requiring purges, and the bimodal distribution problem on budget grinders (Timemore S3, Fellow Opus stock, Baratza Encore) that produces shots tasting simultaneously sour and bitter no matter what setting you choose.
The pull
Dose, yield, time, brew temp. The raw signal of what actually happened in the portafilter.
Ratio (yield divided by dose) tells us how concentrated the shot was. Time tells us about resistance, but not extraction directly. A fast shot can be under-extracted or channelling, and we look at the taste to know which.
The taste
The most important field, and the one most people get wrong because the lexicon is subtle. Sour (bad, under-extraction) is not the same as bright (good, desirable acidity). Bitter (taste, over-extraction) is not the same as astringent (mouthfeel, fines migration). Hollow means the middle of the shot is empty, usually channelling.
See common shot symptoms for a fuller primer.
The goal
One word (sweetness, clarity, body, acidity, balance) to bias the recommendation. Two dial-ins on the same shot with different goals will get different advice. Aiming for sweetness on a light Ethiopian means pushing finer and hotter. Aiming for clarity on the same bean might mean a shorter ratio.