Send Message Input Form resource consumes agent context window, breaking tool discovery

Bug Description

The Send Message Input Form MCP resource (ui://send-message-input.html) shipped with the Slack MCP plugin contains an enormous inline React application (full HTML + JS bundle). When an AI agent fetches this resource to understand the MCP's capabilities, the sheer size of the response consumes the agent's entire context window, preventing it from ever successfully discovering or calling the actual tools (e.g. slack_send_message).

Impact

• The agent sees the resource descriptor and fetches it first, assuming it describes how to send messages
• The fetched HTML is a full React app bundle — far too large and not useful for programmatic tool invocation
• After processing this payload, the agent has no remaining context to discover or call the real MCP tools
• Net result: the Slack MCP integration is effectively non-functional out of the box

Steps to Reproduce

1. Have the Slack MCP plugin enabled in Cursor IDE (default configuration)
2. Ask the AI agent to send a Slack message
3. The agent discovers the Send Message Input Form resource via resources/Send_Message_Input_Form.json
4. Agent fetches ui://send-message-input.html, receives the massive HTML/JS payload
5. Agent gets stuck processing the UI form content and never successfully calls slack_send_message

Expected Behavior

The agent should be able to discover and call slack_send_message (and other tools) without the resource consuming its context window.

Workaround

Manually delete the resource descriptor file from the local MCP metadata:

mcps/plugin-slack-slack/resources/Send_Message_Input_Form.json

After deletion, tool discovery works correctly and slack_send_message sends messages as expected.

Suggested Fix

• Remove the Send Message Input Form resource from the default MCP descriptor set, or
• Gate it behind a UI-only flag that agents skip during tool discovery, or
• Drastically reduce its size so it doesn't overwhelm the context window

Environment

• IDE: Cursor
• MCP Plugin: Slack (plugin-slack-slack)
• Resource: ui://send-message-input.html (described in resources/Send_Message_Input_Form.json)

Start by inspecting resources/Send_Message_Input_Form.json and the referenced ui://send-message-input.html resource in the Slack MCP plugin. Reproduce the Cursor discovery flow and verify that removing or gating this resource lets the agent discover and call slack_send_message without exhausting its context window.