Compare a configured deployment and its operating responsibilities—not a list of platform features. A supplier should first pass your mandatory controls, then compete on verified outcomes and total cost.
Use the same request for proposal for each route:
| Purchasing route | Main question to settle |
|---|---|
| Existing software’s native agent | Does the available configuration cover our exact workflow and exceptions? |
| Configurable voice-agent platform | Who owns integration, testing, monitoring and recovery? |
| Managed vertical service | What is included in the service, and what remains our responsibility? |
| Enterprise conversational deployment | What implementation, governance and service commitments are contractual? |
| Human or hybrid answering | Can it deliver the same verified outcome at a better total cost? |
Support should be compared explicitly. Vapi documents different service commitments by package, including no response or uptime SLA for Usage only. Retell lists enterprise implementation support as an add-on. Neither should be assumed to include a complete managed operating service at its entry usage price. (docs.vapi.ai)
For each supplier request five artefacts: a scope statement, data-flow map, normalised quote, executed test results and an ownership matrix.
Reject a vendor ranking that cannot tell you which tasks, configurations, call conditions and pricing assumptions were compared.