The Tool Desk
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Identify the Copilot integration and failure stage
“Microsoft Copilot API MCP Server” can mean several different setups. Microsoft 365 Copilot plugins can connect to an MCP server or to an API described by an OpenAPI document. Copilot Studio has its own MCP integration and troubleshooting path. The same MCP server may behave differently depending on which host is connecting to it.
Record these three details before editing configuration:
- Host: Microsoft 365 Copilot plugin/app, or Copilot Studio.
- Stage: endpoint connection, authentication/token exchange, tool discovery or validation, or tool invocation.
- Observed symptom: HTTP status, empty Actions list, stuck sign-in popup, or a tool that appears but does not run.
Microsoft’s troubleshooting pages for Microsoft 365 Copilot authentication and MCP apps were last updated July 16, 2026; the plugin authentication overview was updated August 21, 2026. The Copilot Studio troubleshooting page was last updated August 19, 2026. Follow the page for the host you actually use: Microsoft 365 Copilot plugin authentication troubleshooting, MCP apps in Microsoft 365 Copilot, and MCP integration in Copilot Studio.
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Expose the actual error before changing settings
For Microsoft 365 Copilot, enable developer mode and inspect the debug information card in the agent response. Microsoft’s instruction is: “To see authentication errors in agent responses, enable developer mode.” Check the card’s Actions section to see which MCP tools Copilot has available. This separates a sign-in problem from an empty discovery result or a tool invocation failure.
Keep the exact status code or error text, and note whether the tool is absent from Actions or listed but fails when called. An empty list points first to endpoint, authentication, discovery, or validation. A visible tool that does not run is a later-stage problem and should not automatically trigger changes to OAuth registration.
Fix “No tools listed” in Microsoft 365 Copilot
Work through endpoint reachability, authentication, discovery, then manifest validation. A server can be reachable but still return no usable tools if authentication is incomplete or the runtime filters the results.
Confirm the endpoint and authentication
- Verify that the MCP server is running and the plugin manifest’s MCP endpoint URL is the intended endpoint.
- Complete sign-in if the server requires authentication. Some servers return no tools until the user is authenticated.
- Verify that the endpoint responds to MCP discovery and that
tools/listreturns the expected tools.
Check dynamic discovery settings
If the runtime is meant to discover tools dynamically, confirm it is configured with run_for_functions: ["*"] and an empty top-level functions array. Then check that runtime validation has not withheld a tool. If the server returns tools but Copilot still shows none, this configuration and validation path is a more relevant place to inspect than the OAuth redirect settings.
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Check pinned tool declarations
If the manifest pins tools, compare the manifest’s functions entries, descriptions, and run_for_functions tool names with the tools the server actually exposes. A naming mismatch or stale declaration can prevent the expected function from being available even when the MCP service is up.
Repair sign-in and token exchange for Microsoft 365 Copilot plugins
Microsoft identifies mismatches among the OAuth provider, authentication configuration, and plugin manifest as a common source of sign-in failure. Compare all three rather than adjusting one value in isolation.
- Match the base URL. The auth configuration Base URL must match the MCP server
urlin the manifest. For an API plugin, compare it with the relevant OpenAPI server URL instead. - Register the redirect URI. Add
https://teams.microsoft.com/api/platform/v1.0/oAuthRedirectto the OAuth provider’s registered redirect URIs. - Match the reference ID. The runtime’s
auth.reference_idmust match the authentication configuration ID in the Teams developer portal. - Compare app registration IDs. If the error indicates an App ID mismatch, compare the plugin App ID with the OAuth or SSO registration being used.
- Check usage restrictions. Confirm that app and organization restrictions allow the application and tenant to use the integration. An organization-policy denial requires an administrator to review access.
Authentication choices depend on the integration type. Microsoft documents Entra SSO, OAuth 2.0, and anonymous authentication for both MCP and API plugins; dynamic client registration (DCR) for MCP plugins only; and API keys for API plugins only. API-key support for an MCP plugin is not interchangeable with API-plugin support. Agent connector authorization is a separate configuration surface. See Microsoft’s authentication configuration overview before applying a plugin setting to a connector.
Interpret status-specific failures
- HTTP 307 from the token endpoint: Microsoft 365 Copilot’s plugin flow does not support a token endpoint that responds with
307 Temporary Redirect. Configure a direct token endpoint instead of relying on that redirect. - App ID mismatch: Compare the plugin App ID with the OAuth or SSO app registration.
- Base URL mismatch: Make the registered base URL and the manifest’s MCP server URL agree; for an API plugin, use its relevant OpenAPI server URL.
- Missing or incorrect
reference_id: Set it to the matching auth configuration ID in the Teams developer portal. - Organization-policy restriction: Ask the tenant administrator to review the access policy for the app and organization.
Handle consent and SSO separately
For an on-behalf-of flow that needs a user to consent to another API, Microsoft says the server should return 401 Unauthorized to prompt the user to sign in and grant consent. Do not treat that deliberate consent prompt as proof that the MCP endpoint is offline.
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For Entra SSO, check the app’s Application ID URI, the consent redirect URI, and the Microsoft Enterprise token store client against Microsoft’s authentication troubleshooting guidance.
To clear stored OAuth credentials, sign out in Chat settings > Agents. Entra SSO tokens may persist because of caching or tenant/client settings. If you need forced reauthentication, Microsoft points to removing consent or revoking sessions; use the appropriate tenant administration process rather than assuming a local sign-out invalidated every token.
Fix a sign-in popup that authenticates but will not close
Microsoft identifies a destroyed window.opener reference as a likely cause when a popup sign-in appears to finish but never closes. This is a browser redirect-window issue, not necessarily a failed credential exchange.
- Open the popup’s developer tools and inspect
window.openeras the flow moves through its redirects. - Use the Network tab to identify the response whose headers change the popup behavior.
- Inspect redirect-chain JavaScript for code that replaces or loses the opener reference.
- Check whether a response sends
Cross-Origin-Opener-Policy: same-origin. - Check whether the navigation uses
rel="noopener", which prevents the new page from retaining an opener reference.
If the opener is severed during the redirect chain, investigate the page or response responsible for that behavior. Changing the plugin’s tool declarations will not repair a popup that cannot communicate with its opener.
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Check Copilot Studio transport and schema constraints
Do not apply Microsoft 365 plugin-manifest fixes blindly to Copilot Studio. Its documented troubleshooting page identifies transport and schema compatibility constraints that can leave tools unavailable or alter how their inputs are interpreted.
- Open SSE connection endpoint: The endpoint returned by the Open SSE connection call must be a full URI.
exclusiveMinimum: The schema field must be Boolean.type: The field should contain only one type value.- Reference-type inputs or outputs: These are unsupported and filtered.
- Enum inputs: These are interpreted as strings.
Microsoft labels these as known issues and does not provide a workaround for every item. Where a schema feature is unsupported, simplify the schema only if the tool’s contract permits it; otherwise consult the current Copilot Studio guidance rather than assuming an MCP server change will solve the host limitation.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Troubleshoot a tool that appears but does not run
If Actions shows the tool, discovery has succeeded far enough for Copilot to list it. Focus on invocation-specific behavior: confirm that the selected tool name and arguments match its declaration, check the response/error in developer-mode diagnostics, and determine whether the server rejected the request because authentication or consent is needed. For an on-behalf-of consent requirement, the documented prompt is a 401 response, as described above. Avoid changing discovery configuration unless the tool is missing or filtered.
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FAQ
Does “connection failed” mean the MCP server is down?
No. The same symptom can arise at endpoint connection, authentication, discovery, validation, or invocation. Identify the host and stage first.
Are Microsoft 365 Copilot plugins and Copilot Studio MCP connectors configured the same way?
No. They have separate integration surfaces and documented constraints. Use the troubleshooting guidance for the host you are connecting to.
Is a 307 token response supported?
No. Microsoft documents HTTP 307 from the token endpoint as unsupported in the Microsoft 365 Copilot plugin flow.
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