Unable to add MCP Server: Error: Already Exists

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Posted on by DA-15041010-0

Hi everyone,

I’m running into an issue when trying to add an MCP server as a tool inside an agent in Microsoft Copilot Studio.

What I’m doing: I create a new agent (I’ve also tested with existing agents), go to Tools, click “Add a tool”, select “MCP server”, and then enter a unique server name, a unique description, and the server URL (which is a valid MCP endpoint). I leave authentication set to None and click Create.

The issue is that I consistently get the following error: “Something went wrong. A custom connector with display name ‘[name]’ already exists in the environment. It may have been created by another user and may not be visible. Please specify a different name.”

What’s confusing is that this happens regardless of the name I use, even if it’s completely random. I’ve tried multiple different names, multiple agents (both new and existing), and I still get the same error every time. The connectors don’t appear to exist anywhere visible in the environment, so it feels like there may be hidden or orphaned connectors blocking new ones from being created.

Has anyone experienced this before? Is there a way to view or remove hidden or orphaned custom connectors? Could this be a permissions or environment-level issue? Or is there a known workaround to successfully add an MCP server?

Would really appreciate any guidance. Thanks in advance.

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Calling actions from Copilot Studio

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Sunil Kumar Pashikanti 1,681 Moderator on at

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Hi @DA-15041010-0,

Cause
When you add an MCP server in Copilot Studio, the platform automatically creates a Power Platform custom connector behind the scenes. If this process fails or is interrupted, the connector metadata can persist in a system-owned, hidden state. Although it does not appear in the Maker portal, the environment still considers it present, which causes the “custom connector already exists” error when attempting to add any new MCP server.

Copilot Studio MCP integrations explicitly rely on connector infrastructure, even when created through the UI.

Fix

Go to Power Apps Maker Portal > Custom connectors

If a connector related to the MCP server is visible, delete it

Go to Connections and delete any connections referencing that connector

Retry adding the MCP server in Copilot Studio

Important Note
If the connector does not appear in Custom Connectors or Solutions, it is system-owned and cannot be removed manually. In that case, a Microsoft Support ticket is required to purge the orphaned connector metadata at the environment level.

This behavior is consistent with other Power Platform connector failures and is not caused by your MCP server or configuration.

✅ If this answer helped resolve your issue, please mark it as Accepted so it can help others with the same problem.
👍 Feel free to Like the post if you found it useful.

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DA-15041010-0 2 on at

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Hi - thank you very much for responding.

The thing is that there are NO connections or connectors with the same name. This behaviour is consistent even if i make up a random string, for example:

Something went wrong. Please try again.A custom connector with display name '2e21e21edewasdaasd' already exists in the environment. It may have been created by another user or may not be visible to you. Please specify a different name.

Do you have any other suggestions?

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Sayali Microsoft Employee on at

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Hello DA-15041010-0 ,

When you add an MCP server as a tool in Copilot Studio, the platform actually creates a Power Platform custom connector in the background using MCP connector infrastructure—not just a reference to your MCP URL. This means every MCP tool you attempt to onboard results in a new connector being provisioned at the environment level. The error stating that “a custom connector with display name already exists” typically occurs when this background connector creation partially fails but still registers metadata in Dataverse. These failed or incomplete connectors become orphaned environment‑level artifacts that are not bound to any agent and often don’t appear in the Copilot Studio or Power Apps UI. However, because connector display names must be unique across the entire environment, future MCP onboarding attempts fail—even when using completely different or random server names—since the hidden connector entries continue to block new ones.

As a result, you’re encountering an environment-level lifecycle issue rather than a problem with your MCP endpoint or agent setup.
The workaround is to remove these orphaned custom connectors (and any related connection references) from the Power Platform environment using the Power Apps portal or admin tools. After cleanup and allowing time for connector cache refresh, MCP server creation in Copilot Studio usually succeeds. Alternatively, manually creating the MCP custom connector in Power Apps and attaching it to your agent can bypass the MCP onboarding wizard and avoid this provisioning bug entirely.

Reference Document-
1.Microsoft Copilot Studio ❤️ MCP | Power Platform Developer Blog
2.Solved: MCP Server + Custom Connector Issues in Copilot Studio (Tools Not Loading, First Call Fails)
3.Connect your agent to an existing Model Context Protocol (MCP) server - Microsoft Copilot Studio | Microsoft Learn
4.MCP Servers or Connectors in Copilot Studio? A Maker's Guide | The Custom Engine

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Sunil Kumar Pashikanti 1,681 Moderator on at

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Hi @DA-15041010-0,

The fact that this persists even with random strings like '2e21e21edewasdaasd' strongly suggests this is not a true display-name collision. When you add an MCP server, Copilot Studio internally attempts to provision a hidden custom connector. If that background process fails, the platform often defaults to a generic “display name already exists” error message, even if no connector is actually visible.

Recommended Troubleshooting Steps:
1. Verify Data Loss Prevention (DLP) Policies
This is the most frequent cause of "silent" connector failures.

Go to the Power Platform Admin Center > Policies > Data policies.

Check the policy applied to your environment.

Crucial: Ensure that "Custom Connectors" or the "HTTP" conecctor are not blocked or restricted to a "Non-Business" data group that conflicts with where Copilot Studio is trying to operate. If a policy blocks custom connector creation, the MCP onboarding will fail instantly.

2. Audit the "Default Solution"
Sometimes orphaned metadata exists in the solution layer but doesn't surface in the "Custom Connectors" gallery.

Go to Power Apps Maker Portal > Solutions > Default Solution.

Filter by Objects > Custom Connector.

Look for any entries with "Untitled," "Failed," or partial names and delete them.

3. Capture the "Under the Hood" Error
To prove this isn't a naming issue, look at the actual telemetry:

In Copilot Studio, click the Settings (cog icon) > About > Session Details (or press Ctrl+Alt+A).

Look for a PowerPlatformException or FlowOperationError.

If you see a 403 (Forbidden), it confirms a DLP or permissions block. If you see 429, it's a throttling issue.

4. The "Clean Slate" Test
If you have the capacity, try adding the same MCP server in a Developer Environment.

If it works there: Your original environment has a "stuck" metadata state or a restrictive policy.

If it fails there too: There may be a temporary service outage with the MCP-to-Connector bridge in your region.

Next Steps for Support:
If the above steps don't reveal a DLP block, you will likely need to open a support ticket. Be sure to provide your Environment ID and the Session ID from Step 3. Tell them: "The environment is throwing a 'Custom Connector already exists' error for unique random strings, indicating a failure in the internal provisioning of MCP metadata."

Are you using a Managed Environment. If so, there are additional "Developer" limits that can sometimes block the automatic creation of connectors by the Copilot Studio service principal.

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DK-18042228-0 2 on at

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Hi there,

I am having the same issue trying to setup HaloPSA MCP Connection (https://usehalo.com/halopsa/guides/2711/) Please let me know when you find a solution.

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