What's changed: Created PL-400 Chapter 4 (domain: Extend the platform, part 2): custom connectors (Open API definition, auth OAuth/API key/Basic, policy templates, Azure Function, data transformation), platform APIs and Azure Functions (Dataverse Web API OData, Organization service .NET SDK, throttling/retry, OAuth, optimistic concurrency/ExecuteMultiple, Azure Functions long-running/triggers/managed identity), and Power Automate cloud flows (Dataverse connector, expressions, Azure Key Vault, error handling run after, trigger filter/retry, child flows, Entra ID service principal).
4.1Custom connectors
Understand the Open API definition, authentication methods, policy templates, importing from Azure services/GitHub, and data transformation.
A custom connector wraps an external REST API so Power Platform can use it. Design the definition and authentication correctly.
4.1.1Open API definition and authentication
Describe the connector’s API spec with an Open API definition (Swagger) (operations, parameters, responses). Create it by importing from an Azure service, an existing Open API, or GitHub. Choose authentication from OAuth 2.0 / API key / Basic to match the target API. You can also back the connector with an Azure Function for custom logic.
4.1.2Policy templates and data transformation
Policy templates modify connector behavior at runtime—setting/transforming headers, changing the host URL, transforming parameters—without code. For response shaping, add data-transformation code. The Open API (describes the API) and policy templates (change runtime behavior) play different roles.
Cues: "describe REST API operations/parameters/responses" = Open API definition (Swagger). "modify headers/URL/parameters at runtime" = policy templates. "auth via OAuth 2.0/API key/Basic". "custom logic backend" = Azure Function. Custom connector (ingest external API) vs custom API (in-Dataverse op) differ.
Watch the mix-ups: (1) Open API definition (describe API) vs policy templates (change runtime behavior). (2) Custom connector (external API) vs custom API (in-Dataverse). (3) Match the auth method to the target API. (4) Data transformation shapes responses, not the API definition itself.
4.1.3Section summary
- Describe the REST API with an Open API definition (Swagger); import from Azure/GitHub
- Auth = OAuth 2.0/API key/Basic; Azure Function as a backend
- Policy templates change runtime behavior (headers/URL)
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Quick check
(just a quick review)Q1. You want to describe an external REST API’s operations/parameters/responses to define a custom connector. Best?
Q2. In a custom connector, you want to set/transform request headers at runtime without code. Best?
Q3. You want custom logic as the backend of a custom connector. Best?
Q4. Which authentication methods can you choose for a custom connector based on the target API?
Q5. Which correctly distinguishes a custom connector from a custom API?
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