Start with the workflow and the actors
Describe what the system needs to support and who can perform each action. In a multi-tenant product, that includes the boundaries between organizations as well as the permissions within one organization.
The useful question is not simply whether a feature exists. It is whether the right actor can use it, under the right conditions, with an appropriate record of what happened.
Map sensitive data and integrations
Identify what information enters the system, where it moves and which other services it reaches. Payments, identity, email and customer-management integrations can create dependencies that are easy to miss in an interface-only description.
Keep the distinction between a technical control and a compliance conclusion clear. Encryption, access approval and audit trails can be important engineering requirements; they do not automatically create regulatory certification.
Separate responsibilities before services
A multi-service architecture should reflect real responsibilities. Web, API, realtime and background processing may need different operating boundaries. Search and memory services bring their own data and access questions. A service diagram is useful when it explains these decisions, not merely when it contains many boxes.
Define what evidence a change needs
Agree acceptance criteria, relevant regression checks and the information needed for handover. Distinguish a staging reference from a production claim and report-only evidence from direct system inspection. These boundaries make engineering communication more useful.
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