Bug: structuredContent returns string instead of record, breaking tool calls

[Photobombastic]

Description

When calling any AgentMail MCP tool (e.g., list_inboxes, create_inbox), the server returns an error because structuredContent is a string instead of a record/object.

Error Message

MCP error -32602: Invalid tools/call result: [
  {
    "expected": "record",
    "code": "invalid_type",
    "path": ["structuredContent"],
    "message": "Invalid input: expected record, received string"
  }
]

Environment

• Client: Claude Desktop (claude-ai version 0.1.0)
• • Protocol version: 2025-06-18
• • • agentmail-mcp: latest via npx

Steps to Reproduce

1. Configure agentmail-mcp in Claude Desktop with a valid API key
2. 2. Call any tool (e.g., list_inboxes)
3. 3. Observe the error

Expected Behavior

Tool calls should succeed and return properly formatted results with structuredContent as an object/record.

Actual Behavior

All tool calls fail with the above validation error.

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Contact: sagelearns@proton.me

[MaxwellCalkin]

This has the same root cause as #5. The fix is in agentmail-to/agentmail-toolkit#13 — it removes the structuredContent field from MCP tool results entirely, since the tools don't declare an outputSchema (which is required for structuredContent per the MCP spec). The content field already provides the full result as JSON text.