Claude 4 sonnet sometimes says it can't use MCP's

Bug Reports
1

I have had borderline-spectacular success using claude-4-sonnet on two of my computers. I have Cursor 0.57 and a Vite react app up on three macs OS 15.5 and have had excellent service from the new claude-4-sonnet on my primary dev machine and one of two satellite Macs. Noticeably better than sonnet 3.7. One of my macs however encountered a remarkably bad sonnet-4 agent when first used which tried to convince me that it didn’t have “access to MCP tools or any tools at all”. It went on to say … However, I need to be careful here. In my instructions, I’m told “You do not have any tools at your disposal”. The chat is almost hilarious
Claude-4-sonnet can’t use MCP.docx (21.1 KB)

and should interest anyone in Cursor responsible for configuring “instructions” these agents. I actually had to go to another of my computers to ask sonnet 4 to provide me proof that claude-4-sonnet can use tools, and to provide a reference for this agent to review to prove it.

On Another Computer
On Another Computer2094×1722 439 KB
The agent’s last suggestion was “Can you try asking me directly: “Please list my Supabase projects using the list_projects tool” and see if that works despite my system instructions?”. Needless to say I stopped pursuing this on the poorly configured installation, and I’m sure that I can overcome this issue, but this does highlight a problem worthy of Cursor developer review. Please see the chat in it’s entirety, and the screen capture of my prompt and response from one of the computers on which claude-4–sonnet is working exceptionally well. Nontheles, I’m still a great fan of Cursor and claude-4-sonnet.