n8n MCP Client Tool with mcp-atlassian

[aleksi-p]

I am using n8n with the MCP Client Tool and want to use the mcp-atlassian server to connect to Jira & Confluence Data Center. Well, connection works, but I have some missmatch. Anyone an idea?

Error calling tool 'search': 4 tool_manager.py:129 mcp_atlassian | validation errors for mcp_atlassian | call[search] mcp_atlassian | sessionId mcp_atlassian | Unexpected keyword argument

╭─ Traceback (most recent cal─╮
│ /app/.venv/lib/python3.10/s │
│ ite-packages/fastmcp/tools/ │
│ tool_manager.py:120 in │
│ call_tool │
│ │
│ 117 │ │ │ raise Not │
│ 118 │ │ │
│ 119 │ │ try: │
│ ❱ 120 │ │ │ return aw │
│ 121 │ │ │
│ 122 │ │ # raise ToolE │
│ 123 │ │ except ToolEr │
│ │

[samkitjain17]

I'm running into MCP from the n8n side as well, and the key part of your stack trace is this bit:

validation errors for mcp_atlassian | call[search] mcp_atlassian | sessionId | Unexpected keyword argument

That usually means:

• the search tool in mcp-atlassian has a fixed JSON schema for its arguments
• the MCP client (n8n / fastmcp) is sending an extra field – here sessionId
• Pydantic on the server side rejects it because sessionId isn't a valid argument for that tool

---

Things to check

1. Inspect the tool schema

List and inspect the search tool definition from mcp-atlassian using your MCP client or CLI. That will show you exactly which fields are allowed (e.g. query, filters, etc.). You should not see sessionId there.

2. Check your n8n MCP node config

In the n8n MCP Client Tool:

• Make sure only fields that exist in the search tool schema are passed into arguments
• If sessionId is being added as custom metadata, it must not go into the tool arguments payload

3. Minimal repro test

Try calling search with the smallest valid payload (only the required schema fields). If that works, add fields back one by one until the failure shows up again, which will likely be sessionId.

---

If you're doing a lot of MCP + Jira/Confluence experiments and don't want to keep debugging client-side validation mismatches like this, I've also had good luck testing and hosting MCP servers through MCPfy, it gives you a UI to inspect tool schemas, run test calls, and validate arguments before wiring them into clients like n8n. It's helped me catch these exact "unexpected keyword argument" issues earlier.

Happy to compare configs if you're okay sharing your n8n MCP node setup (minus secrets).