Designing Platform Extensions: Connectors, Plug-ins & APIs

Extending the platform’s brain

Custom connector design

A custom connector bridges Power Platform to any REST API. Design decisions include authentication, actions, triggers, and policies.

When to build a custom connector

• The external API does not have a built-in Power Platform connector
• You need to expose specific API operations to makers (not the full API surface)
• You want to standardise how your organisation connects to a particular service
• An ISV wants to publish a connector for their service

Design considerations

Design Area	Questions to Answer
Authentication	OAuth 2.0, API Key, or Basic? Who manages the credentials? Per-user or shared?
Actions	Which API endpoints to expose? How to name them clearly for makers?
Triggers	Does the API support webhooks for real-time triggers? Or polling?
Data transformation	Do responses need to be reshaped? Are there pagination patterns?
DLP classification	Which DLP group should this connector be in? (Custom connectors default to Non-business)
Error handling	How does the API report errors? Do you need policy templates to standardise responses?

💡 Scenario: Marcus designs a connector for NovaSoft's product API

Marcus Chen at NovaSoft Solutions builds a custom connector for NovaSoft’s product catalogue API. His design decisions:

• Auth: OAuth 2.0 (each user authenticates with their NovaSoft account — per-user, not shared credentials)
• Actions: GetProducts, GetProductById, UpdateInventory — only 3 of the API’s 20 endpoints, keeping it simple for makers
• Triggers: Webhook-based trigger for “product price changed” events
• Data transform: API returns nested JSON; Marcus adds a policy template to flatten the response for easier use in Power Automate
• DLP: Requests the admin classify it as Business (it handles business inventory data)

Plug-in vs custom API vs Power Fx function

These three all add server-side logic to Dataverse, but they serve different purposes.

Three approaches to server-side logic — choose based on trigger, audience, and complexity

Factor	Plug-in	Custom API	Power Fx Function
Language	C#	C# (backed by plug-in)	Power Fx (low-code)
Trigger	Dataverse events (create, update, delete, etc.)	On-demand (called explicitly)	On-demand (called from apps/flows)
Callable from outside?	No — event-driven only	Yes — Web API, SDK, flows, apps	Yes — flows and apps
Transaction context	Runs within the Dataverse pipeline transaction	Can run in or outside a transaction	Runs within platform context
Complexity	Full C# — any logic, Organisation service	Full C# — plus custom request/response	Power Fx — limited to supported functions
Solution-aware	Yes	Yes	Yes
Best for	Intercepting data events, validation, enrichment	Reusable business operations, external-facing endpoints	Simple server-side logic accessible to makers

Decision guide

• Need to react to a data event (record created, updated, deleted)? → Plug-in
• Need a reusable operation that apps, flows, or external systems can call? → Custom API
• Need server-side logic but want makers to maintain it? → Power Fx function
• Need a plug-in AND want it callable on demand? → Custom API backed by a plug-in (best of both)

Question

What is a custom API in Dataverse?

Click or press Enter to reveal answer

Answer

A custom API defines a new message (endpoint) on Dataverse that can be called from apps, flows, Web API, or SDK. It has defined request parameters and response properties. It is backed by a plug-in that implements the business logic. Unlike standard plug-ins, custom APIs are callable on demand, not just triggered by data events.

Click to flip back

Question

What is a Power Fx low-code plug-in?

Click or press Enter to reveal answer

Answer

A Power Fx function that runs server-side in Dataverse. It allows makers to write business logic using Power Fx formulas instead of C#. It is more limited than C# plug-ins but accessible to low-code developers who cannot write C#. It can be triggered from apps and flows.

Click to flip back

Question

When should you choose a custom connector over a direct API call?

Click or press Enter to reveal answer

Answer

Use a custom connector when: (1) you want the API available to makers in canvas apps and Power Automate, (2) you need to standardise authentication and error handling, (3) you want the connection to be manageable through the admin centre, (4) multiple apps and flows will use the same API.

Click to flip back

Knowledge Check

Amara needs to implement a 'Calculate shipping cost' operation for a logistics client. The operation takes package dimensions, weight, and destination as input and returns a cost. It must be callable from canvas apps, cloud flows, and external ERP systems via API. Which approach should she use?

AA Dataverse plug-in registered on the Create message of a Shipping tableBA custom API backed by a C# plug-inCA Power Fx low-code functionDA custom connector calling an Azure Function

Check Answer

Knowledge Check

A developer builds a Dataverse plug-in that validates order data before save. The product team also wants the same validation logic to be available as an API endpoint for the company's external web portal. What is the best approach?

ARegister the same plug-in on two different messagesBCreate a custom API that calls the same validation logic, and register the plug-in on the Order Create message as wellCDuplicate the validation code — one plug-in for Dataverse events, one Azure Function for the web portalDExpose the plug-in directly via a webhook

Check Answer

🎬 Video coming soon

Next up: Integration & Automation Blueprints — designing cloud flows and Dataverse-to-Azure integration patterns.