Ensure the property field exists in tool input schemas

[pushpak1300]

Problem

When a Tool has no input parameters, JsonSchema’s serializer omits the properties field entirely. While the MCP specification doesn’t explicitly require properties to be present, some strict model providers (like GPT-5) expect it and fail with “invalid argument” errors when it’s missing.

Solution

Explicitly set properties to an empty object {} when not present to ensure maximum compatibility with strict JSON Schema validators.

Testing

1. Create a tool with no input parameters.
2. Connect using Windsurf with GPT-5 models.
3. Verify the tool loads without errors.

Fixes: laravel/boost#278