Hey, thanks for the report. This is a known issue. A few users have already run into it, including with GitHub MCP and other servers.
What’s happening: the CallMcpTool schema supports arguments, but the model sometimes doesn’t fill that field during automatic MCP tool calls. Your second case with corrupted JSON using “arentId” instead of “parentId” is also a known variant and seems related to serialization.
The team is aware. As a workaround:
- Add a clear instruction in your rules or skills about the call format:
When calling Linear MCP save_issue, ALWAYS include all arguments in the arguments object:
{"server": "linear", "toolName": "save_issue", "arguments": {"title": "...", "teamId": "...", ...}}
NEVER call save_issue without the arguments field.
- Try a different model instead of Auto. Behavior varies by model.
Related threads with more details:
- MCP tool called without required "key" arg during Agent auto-call, manual call works
- Regression: agent can no longer create PRs via GitHub MCP (`create_pull_request` without arguments)
Let me know if the workaround helps.