The default chat widget that comes with a Copilot Studio agent is fine for many sites. It drops into the corner, it works, and it gets the job done. But sometimes fine is not enough. Maybe you want the chat to match your brand exactly, sit inside a specific part of the page, or behave in a way the standard widget does not allow. For that level of control, you use the Agent API to build your own custom interface.
Why Go Beyond the Default Widget
The built-in widget is quick to add, but it puts you inside a box. You get limited say over how it looks and where it sits. For a polished, branded site, that box can feel out of place. A custom interface lets you control everything: the colors, the shape of the chat bubbles, where the chat appears, and how it fits into your page flow.
The Agent API is what makes this possible. It connects your own web design to the brains of your Copilot Studio agent. You build the look and feel, and the API handles the conversation underneath. The result is a chat that feels like a true part of your site, not a bolted-on extra.
What the Agent API Gives You
The Agent API bridges your low-code Power Pages experience with the intelligence of your Copilot Studio agent. Instead of being stuck with the default chat, you can embed a branded conversation interface right into your pages, forms, and workflows. You send the visitor’s messages to the agent through the API, and you get the agent’s replies back to display however you like.
This means you can build chat bubbles, sidebars, inline help cards, or pop-up assistants that match your site exactly. The conversation runs on the agent you already built, but the experience around it is entirely yours to shape.
Step One: Get the Agent Ready
Before you build any custom interface, make sure the agent itself is solid. Build and test your topics in Copilot Studio, set up any knowledge sources, and confirm the agent answers well. The custom interface is just the face. The agent behind it still does the thinking, so it needs to be working properly first.
It also helps to plan your authentication at this stage. If your custom chat should only work for signed-in users, decide how identity will flow before you start building the front end. Sorting this out early saves rework later.
Step Two: Connect Your Interface to the Agent
With the agent ready, you build your own chat interface using web technology like HTML and JavaScript, and you connect it to the agent through the API. Your interface sends what the visitor types to the agent and shows the agent’s responses on the page. You control the layout, the styling, and the behavior, while the API carries the conversation back and forth.
This is where your design comes to life. You decide whether the chat is a floating bubble, a panel that slides in, or a section built into the page. Because you own the markup and styles, it can look exactly like the rest of your brand.
Step Three: Pass Context for a Personal Touch
One big benefit of a custom interface is that you can pass useful context to the agent, like the signed-in user’s details or the page they are on. When you send this context along with the conversation, the agent can tailor its replies. It can greet the person by name or focus on the topic of the current page. This makes the custom chat feel sharp and aware.
Passing context well is what separates a basic custom chat from a great one. The more the agent knows about the situation, the more helpful and personal it can be.
Step Four: Handle Authentication Carefully
Because a custom interface gives you more control, it also gives you more responsibility around security. You manage how the connection to the agent is set up, often through a token exchanged when the page loads. Make sure this is done in a way that protects your agent and your data. If the chat should only serve signed-in users, tie the connection to their login so anonymous visitors cannot reach it.
Take this part seriously. The flexibility of a custom build is wonderful, but it means the safe defaults of the standard widget are now in your hands.
Test Across Devices and States
Once your custom chat is built, test it thoroughly. Check how it looks and works on a desktop and on a phone, since a custom layout can behave differently on small screens. Test it signed in and signed out if that matters. Run through real conversations to confirm the agent replies correctly and that your interface shows everything cleanly.
Watch for visual glitches, like text that overflows or buttons that do not line up. A custom interface only shines when it is polished, so spend the time to get the details right.
Wrapping Up
The Agent API lets you move past the default chat widget and build a Copilot Studio experience that truly fits your Power Pages site. You get the agent working first, connect your own HTML and JavaScript interface through the API, pass along context for a personal touch, and handle authentication with care. Test across devices and states, polish the details, and you end up with a chat that looks and feels like a natural part of your brand, powered by the agent you already built.