Short of something structured, any format that captures key assumptions and intentions is good. The problem we are solving is X. The "pre-mortem" is the idea is

Short of something structured, any format that captures key assumptions and intentions is good. The problem we are solving is X. The "pre-mortem" is the idea is that if we fail, it would be because of Y. Then in your design or decision, you address Y as a contingency. The collateral idea for code would be "good until" - this is good until (we expect) some threshold.