As outlined in the AgentForce External Services and Prompt Flow Integration Guide, when data is retrieved from a registered external service via REST API, the response payload is stored as External Service Records. These records can then be referenced dynamically within prompt templates through External Service Record merge fields.

This approach allows the large language model (LLM) to use the fetched data as contextual grounding during prompt execution, ensuring that generated responses are accurate and consistent with the latest API results.

Option B is incorrect because AgentForce does not use XML merge fields for API responses; JSON data is automatically mapped to object structures. Option C is also incorrect — the “Add Prompt Instructions” element modifies prompt context or tone but does not pass external data for merge use.

Therefore, the correct method is Option A – Use External Service Record merge fields, ensuring the external service data is directly available for prompt templates.