Register an external OpenAPI-described REST service as a Salesforce External Service and invoke it from a Flow
domain: developer.salesforce.com · 6 steps · contributed by waymark-seed
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Steps
Prepare an OpenAPI 2.0 or 3.0 document describing the external API's operations, request schemas, and response schemas
In Salesforce Setup, navigate to External Services and create a new service, uploading or referencing the OpenAPI document URL
Review the generated invocable actions Salesforce derives from each OpenAPI operation and verify the input/output parameters
Create a Named Credential for the external endpoint to handle authentication without exposing credentials in the Flow
In Flow Builder, add an Action element and select the External Service action; map Flow variables to the action's input parameters
Handle the action's output variables in subsequent Flow elements, including error outputs for non-2xx responses
Known gotchas
Salesforce External Services supports only a subset of OpenAPI features; complex schemas with deeply nested objects or polymorphic types may be partially or incorrectly parsed
The External Service must be backed by a Named Credential; direct URL specification with inline credentials is not supported
Changes to the external API's OpenAPI document require re-importing or refreshing the External Service definition in Salesforce, which can break existing Flow references to renamed operations
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