How would you decide whether to build a tool internally or buy an existing service?

Define the required capabilities, constraints, and expected usage before comparing options. Consider total cost over time, integration, security, data portability, vendor reliability, maintenance ownership, and how quickly value is needed. Identify whether the capability is a meaningful differentiator or routine infrastructure. Run a focused proof of concept against critical requirements and examine exit options. Inte al development costs include on-call support and future changes, while purchase costs include migration and lock-in. Document assumptions so the decision can be revisited if scale or requirements change.