Built-in MCP servers show as connected, but Agent in Interact Mode cannot access or invoke tools

[Volejo]

Hello

I am trying to use the Builder.io Agent in Interact Mode with the built-in MCP servers enabled.

The MCP servers appear to be connected in the Builder settings, but the Agent does not seem to have access to them or cannot invoke their tools.

For example:

• Supabase appears as connected, but the Agent cannot access Supabase or use the database-related functions.

• I do not receive any Supabase authentication request or authorization flow.

• Semgrep also appears to be connected, but it does not seem to work from the Agent either.

• In the settings, the only available option for these MCP servers is “Disable”, which makes it look like they are already connected.

Expected behavior
If a built-in MCP server is shown as connected, I would expect the Agent in Interact Mode to be able to access its tools, request authentication if required, and use the connected service.

Actual behavior
The MCP servers are shown as connected in the UI, but the Agent behaves as if the MCP tools are not available. No authentication prompt appears for Supabase, and the Agent cannot use the connected MCP functionality.

Code stack you are integrating Builder with
Builder.io landing page built with TypeScript and deployed via Netlify.

Reproducible steps

1. Open Builder.io project.

2. Go to settings / MCP servers.

3. Enable or connect the built-in Supabase MCP server.

4. Confirm that Supabase appears as connected.

5. Open the Builder Agent in Interact Mode.

6. Ask the Agent to access or use Supabase.

7. No authentication request appears, and the Agent cannot access or invoke Supabase tools.

8. The same issue seems to happen with Semgrep.

Question
Is there an additional step required to make built-in MCP servers available to the Agent in Interact Mode, or is this a bug with the MCP connection status?

Best Val

[Volejo]

Summary of the MCP Server Access Issue (written by the ai bot)

I’ve been working extensively with the Builder.io Agent in Interact Mode and can confirm this is indeed a significant limitation. Here’s what I’ve discovered:

Problem Confirmation:

• MCP servers (Supabase, Semgrep) display as “Connected” in settings
• The Agent cannot automatically invoke their tools or access their functionality
• No authentication flows are triggered
• The connected status appears to be UI-only, not functional

Specific Examples Encountered:

1. Supabase: Cannot execute SQL queries, create RLS policies, or perform database operations through the Agent
2. Semgrep: Cannot run security scans on code despite being marked as connected
3. General Pattern: Tool search returns no Supabase/Semgrep-specific tools available to the Agent

Current Workarounds:

• Execute Supabase queries manually via SQL Editor in dashboard
• Use credentials directly with API calls via Bash tool
• Perform manual code reviews instead of automated scanning
• Direct CLI usage when ACL policies permit

Root Cause Analysis:
The “Connected” status likely indicates only basic UI registration, not full MCP protocol implementation for the Agent. Built-in MCP servers may require additional authentication setup or configuration that isn’t currently automated in Interact Mode.

Recommendation:
This appears to be either:

1. A bug in MCP tool availability in Interact Mode
2. Missing documentation on required setup steps
3. Incomplete MCP protocol implementation for these specific servers

Would be helpful to clarify from the Builder.io team whether this is expected behavior or if there’s an additional step needed.

[Volejo]

@ParthSharma

do you have an idea?

[Volejo]

Is there anyone who is able to help? Would much appriciate it. Thanks.

[ParthSharma]

Hi Val,

Thank you for the detailed report and for your patience! We’re sorry for the delay in getting back to you.

To make sure our team can look into this as quickly as possible, could you please do the following:

1. Send an email to support@builder.io with the details of this issue so it gets picked up by our support team right away.
2. Share your Builder.io project URL (in the email) so we can directly inspect the MCP configuration and replicate the behaviour on our end.

This will help us investigate and get you a resolution much faster. Looking forward to hearing from you!

Best regards,

[Volejo]

Hi Parth,

thank you for your message.

I just solved the problem yesterday by myself.

The mcp’s were not authorized in the fusion settings on the fusion overview chat section.

i expected all the settings on this site. Here should also be a opportunity to start the auth process. Its not very logical for the user.