fix: support structuredContent in MCP tool responses

[layer4down]

Summary

Fixes issue #469 where MCP web search tools (e.g., victor/websearch HuggingFace Space) returned empty output despite successful tool execution.

Problem

MCP web search servers return results in the structuredContent field of CallToolResult, but the _extract_content method only checked the content field, resulting in empty responses.

Solution

Modified _extract_content in omlx/mcp/client.py to fall back to structuredContent when content is empty or not present.

Changes

• omlx/mcp/client.py: Added structuredContent fallback in _extract_content method (lines 359-361)
• tests/test_mcp_client.py: Added test case test_call_tool_structured_content to verify the fix

Testing

All 36 MCP client tests pass, including the new test:

tests/test_mcp_client.py: 36/36 passed (including test_call_tool_structured_content)

Related

Closes #469

[jundot]

thanks for the contribution! the core idea — falling back to structuredContent when content is empty — is solid and aligns with the MCP spec.

i cherry-picked the key logic change (structuredContent fallback in _extract_content) and the formatting fixes into main directly at 3171bd3, with you as co-author.

a couple notes on why i didn't merge the PR as-is:

• issue [MCP] Web search returns no output #469 was actually a client-side problem (Open WebUI not executing tools via /v1/mcp/execute), not a missing structuredContent issue. the PR description links to it but the fix doesn't address the original report
• tests/test_structured_content.py duplicated tests already in test_mcp_client.py and had inline imports (project convention requires top-level imports)

your contribution is credited in the commit. appreciate the PR!