Fix optional arrays/objects issue #771

[JMLX42]

Disclaimer

PR/patches written with Claude Code (Sonnet 4)

Summary

Fixes MCP Inspector sending empty arrays [] and objects {} for optional parameters instead of omitting them, which causes compatibility issues with OpenAPI servers.

Problem

• MCP Inspector was automatically sending empty arrays [] for optional array parameters
• MCP Inspector was automatically sending empty objects {} for optional object parameters
• OpenAPI servers expect optional parameters to be completely absent when not specified
• This caused API calls to fail or behave unexpectedly

Solution

Updated the generateDefaultValue function in schemaUtils.ts to:

• Return undefined for optional array parameters (omits them from requests)
• Return undefined for optional object parameters (omits them from requests)
• Continue returning [] for required array parameters
• Continue returning {} for required object parameters

Implementation Plan

• Fix array handling: Update array case to check if property is required, returning [] only for required arrays and undefined for optional arrays
• Fix object handling: Update object case to check if property is required, returning {} only for required objects and undefined for optional objects
• Add comprehensive tests: Ensure both required and non-required cases are tested for arrays and objects
• Verify consistency: Make sure array and object behavior aligns with other optional types (string, number, boolean)
• Commit structure: Create separate fix: commits for arrays and objects as requested

Testing

Added comprehensive test coverage for:

• Optional arrays → undefined
• Required arrays → []
• Optional objects → undefined
• Required objects → {}
• Non-required arrays in parent schema → undefined
• Non-required objects in parent schema → undefined

All existing tests continue to pass, ensuring no regression.

Expected Outcome

Optional array and object parameters will be omitted from tool call arguments instead of being sent as empty arrays/objects, resolving compatibility issues with OpenAPI servers.

Fixes #771