Build it around a weighted, evidence-based scoring model so your shortlist is defensible. Start by mapping your must-haves to a framework like NIST CSF or ISO 27001 so every vendor answers against the same baseline.
then structure sections around company stability, technical capability against your controls, integration with ur stack (siem, iam, edr), certs like soc 2 type II and iso 27001, incident response and slas, and pricing. make the security questionnaire require evidence and test results not yes/no claims, and set minimum thresholds on the non-negotiables so weak vendors drop before demos
weight the scoring BEFORE u see responses or u'll just end up fitting scores to the vendor u already liked lol