Composer 1.5 frequently fails to detect and run MCP tools. It tried to access resources using normal web-based URLs and fails with messages that say “URL requires login, cannot access”. MCP servers give access to such internal URLs.
Steps to Reproduce
Install several MCP servers, and ask composer to specifically do something that requires MCP access.
Expected Behavior
All models in cursor, including Composer 1.5 are able to use MCP tools effectively without mistakes.
Hey, thanks for the report. This is a known limitation in Composer 1.5 when working with MCP tools. Instead of calling MCP tools, it tries to access resources directly via URL. A similar bug has already been reported here: Composer 1.5 cannot see full response from Figma official MCP
For now, the workaround is to use Claude Sonnet 4.6, Opus 4.6, or GPT 5.3 Codex for tasks that require MCP. These models call MCP tools correctly.
A few questions to help us debug:
Which MCP servers do you have configured?
Do other models (Claude, GPT) work with the same MCP servers without issues?
Can you share the Request ID from the chat where Composer 1.5 didn’t use MCP? Click the three dots in the top right of the chat, then Copy Request ID.
The team is aware of the issue. Your report helps us prioritize it.
Yup. This is what I figured out after trial and error. Thanks for confirming
Internally developed.
Yup.
I don’t have that. I just reuse the same chat prompt by resubmitting old prompt with new model (why keep stale conversation in the history). But I keep observing this problem. Specially this get really annoying in ‘Auto’ mode where cursor tries to use composer and keeps failing. Looking at thinking trace and other behaviors we can infer which model the auto is trying to use. I think this should be fixed with high priority because cursor advertises and recommends people to use ‘Auto’ to control costs.
