An agent can produce a plausible answer while taking an incorrect execution path. Tool calling therefore needs to be tested as a first-class quality surface.
Validate tool selection
For each business journey, define which tools are allowed, required or prohibited. Verify that the agent selects the appropriate capability for the user's request.
Validate parameters
Check required arguments, data types, values, authentication context and business constraints. A correct tool called with the wrong identifier can still create a serious defect.
Validate sequence and recovery
Test whether tools are called in an acceptable order and whether timeouts, empty responses, retries and downstream errors lead to safe recovery rather than uncontrolled behaviour.
Test handoffs
When an agent transfers work to another agent, workflow or human, verify that the destination is correct and that the relevant context is preserved.
Need this applied to your AI system?
Turn the principle into an assessment, test strategy or engineering engagement.