Keynesians
1)"Start with spending goals
2) Set tax policy to realize adequate revenue"
MMT
1) Start with spending goals
2) Evaluate inflation risk
3) Set tax policy (or carveouts) to minimize inflation risk
It's just plain vanilla PAYGO
You could easily end up with highly inflationary DEFICIT NEUTRAL spending, e.g. doing a massive infrastructure bill "paid for" with a wealth tax or something.