AWS Marketplace MCP server connects by default and cannot be disconnected via Web UI

Summary

The AWS Marketplace built-in MCP server (mcp__claude_ai_AWS_Marketplace__*) is marked as connected by default in the Claude.ai Web UI. Clicking Disconnect has no effect — it reconnects automatically on the next session or immediately.

Impact: HIGH / Financial

This is a high-priority issue because:

• The server's tool definitions are injected into the context window on every conversation
• Users are being charged for token usage they explicitly opted out of
• There is no functional way to prevent this through the UI or local config (~/.claude/settings.json deny rules block execution but do not prevent the tools from loading into context)

Steps to Reproduce

1. Open Claude.ai Web UI or Claude Code
2. Navigate to MCP server settings
3. Observe AWS Marketplace MCP is connected by default
4. Click Disconnect
5. Observe: server reconnects / disconnect has no persistent effect

Expected Behavior

• Users should be able to permanently disconnect built-in MCP integrations
• Disconnected servers should not load tool definitions into context (no token cost)

Actual Behavior

• Disconnect does nothing; server remains connected
• Tool definitions (mcp__claude_ai_AWS_Marketplace__*) appear in every conversation's available tools
• Users incur token costs for tools they explicitly do not want

Workaround (Partial)

Adding a deny rule to ~/.claude/settings.json blocks execution but does not remove the tools from context or eliminate the token overhead:

{
  "permissions": {
    "deny": ["mcp__claude_ai_AWS_Marketplace__*"]
  }
}

Environment

• Platform: macOS Darwin 25.2.0
• Shell: zsh
• Claude Code model: claude-sonnet-4-6