Renata is building a Copilot Studio agent for Sundown Hotels that allows guests to extend their stay. The topic collects the guest's reservation ID (stored in 'Topic.ReservationID') and the additional number of nights (stored in 'Topic.ExtraNights'). Renata has created a Power Automate cloud flow with the 'Run a flow from Copilot' trigger that has two input parameters: 'ReservationID' (Text) and 'ExtraNights' (Number). How does Renata correctly pass the topic variable values to the cloud flow when calling it from the topic?
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Short Explanation
Treat the 'Call an action' node like a phone call — you dial the flow, then you explicitly say which values go where. Open the input parameters, use the variable picker, and bind Topic.ReservationID to ReservationID and Topic.ExtraNights to ExtraNights. Nothing flows automatically.
Full Explanation
When a Copilot Studio topic invokes a Power Automate cloud flow via a 'Call an action' node, parameter values must be explicitly mapped from topic variables to the flow's input parameters. This mapping is done inside the 'Call an action' node's configuration panel. The correct approach is to expand the input parameters section in the 'Call an action' node that invokes the flow and map 'Topic.ReservationID' to the 'ReservationID' parameter and 'Topic.ExtraNights' to the 'ExtraNights' parameter using the variable picker. After selecting the flow, Copilot Studio renders the flow's input parameter list — 'ReservationID' and 'ExtraNights'. The developer uses the variable picker (the formula bar or brace syntax) to map each parameter: 'ReservationID' receives the value of 'Topic.ReservationID', and 'ExtraNights' receives the value of 'Topic.ExtraNights'. The types must be compatible — Text to Text and Number to Number — or Copilot Studio will flag a type mismatch error. The approach that leaves the input fields empty is incorrect because Copilot Studio does not automatically inject conversation variables into cloud flow parameters. The agent runtime and the flow runtime are separate — the flow cannot introspect the agent's variable store without explicit parameter passing. The approach that hardcodes the reservation ID and extra nights as default values in the flow trigger is incorrect because it makes the flow inflexible — every guest would receive the same hardcoded reservation ID and night count. Default values in flow triggers are only used when no value is passed from the calling agent, serving as fallbacks rather than dynamic mappings. The approach that adds a 'Send an HTTP request' node before the 'Call an action' node to POST the topic variables to the flow's trigger endpoint, then references the flow action only to retrieve the response, is incorrect because it is an anti-pattern that duplicates effort and bypasses the built-in parameter mapping mechanism. The 'Call an action' node handles data passing natively — no pre-flight HTTP request is needed or appropriate. Exam tip: Parameter mapping in 'Call an action' nodes is explicit and bidirectional. Inputs flow from topic variables to the flow, and outputs flow from the flow back to topic output variables. Both directions require explicit configuration — neither is automatic.