Azure MCP Server Returns Non-JSON-RPC Format, Breaking Docker MCP Gateway Integration

[NotMyself]

Summary

The Azure MCP server returns a custom JSON response format instead of JSON-RPC 2.0, causing all tool calls through Docker MCP gateway to fail with invalid character 'S' looking for beginning of value.

Full Bug Report

See detailed analysis and reproduction steps at:
NotMyself/claude-hall-monitor#1

Quick Summary

When running via Docker MCP gateway (docker mcp server enable azure):

• Azure MCP returns {"status":200,"message":"Success",...} instead of JSON-RPC 2.0
• The 'S' in "Success" breaks the JSON-RPC parser
• Azure CLI works fine (authentication is valid)
• Other MCP servers work fine (gateway is valid)

Direct Container Test

echo '{"jsonrpc":"2.0","id":1,"method":"tools/list"}' | docker run --rm -i mcp/azure server start

Returns:

{"status":200,"message":"Success","results":[],"duration":89}

Should return:

{"jsonrpc":"2.0","id":1,"result":{"tools":[...]}}

Related Issues

This may be related to the authentication regression in versions 0.6.x-0.8.x (#776) where stderr/stdout contamination was also reported.

Environment

• Docker Desktop: Latest (December 2025)
• Azure CLI: Authenticated and working
• OS: Windows 11

Cross-References

• Also reported to: docker/mcp-gateway, Azure/azure-mcp

[joshfree]

Thanks for reporting this, @NotMyself. @conniey can you follow up on this regression and also see what regression test could be added?