Slack MCP integration tool names exceed 64-character API limit

Bug Description

When using Slack MCP integration in Claude.ai web app, some tool names exceed the 64-character tool_name API limit, causing invalid_request_error.

Error Message

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.2.content.0.tool_result.content.2.tool_reference.tool_name: String should have at most 64 characters"},"request_id":"req_011CXkDk6HcgTXk3L6zppBJC"}

Root Cause

MCP integration tool names are constructed as mcp__<UUID>__<tool_name>. When the UUID prefix (mcp__9b268f53-0be3-4f4f-8b58-9c311a608b58__) is combined with longer tool names, the total exceeds 64 characters.

Affected tools:

| Tool name | Total length | Over limit |
|-----------|-------------|------------|
| mcp__9b268f53-...__slack_search_public_and_private | 74 chars | +10 |
| mcp__9b268f53-...__slack_send_message_draft | 67 chars | +3 |
| mcp__9b268f53-...__slack_read_user_profile | 66 chars | +2 |

Tools that barely fit:

| Tool name | Total length |
|-----------|-------------|
| mcp__9b268f53-...__slack_search_channels | 64 chars (exactly at limit) |

Steps to Reproduce

1. Enable Slack MCP integration in Claude.ai web app
2. Ask Claude to search Slack channels or read user profiles
3. Claude attempts to call the affected tools → API returns 400 error

Expected Behavior

All MCP tool names should stay within the 64-character API limit.

Suggested Fix

• Shorten the UUID prefix (e.g., use first 8 chars instead of full UUID)
• Or shorten the Slack tool names (slack_search_public_and_private → slack_search_all, etc.)
• Or increase the API tool_name character limit

Environment

• Platform: Claude.ai web app (claude.ai)
• Model: Claude Opus 4.5
• Date: 2026-02-03