Preserve native JSON types when passing arguments to tool handlers #587

Is your feature request related to a problem? Please describe.

The SDK currently converts JSON objects into associative PHP arrays before passing them to tool handlers. This forces a specific PHP representation on consumers instead of preserving the original JSON types.

Describe the solution you'd like

Pass validated arguments to tool handlers without implicit type conversion:

• JSON objects → stdClass
• JSON arrays → array
• Scalar values → their corresponding PHP types

This should apply recursively to nested structures.

For consumers preferring associative arrays, the SDK could provide an optional, documented recursive stdClass-to-array converter. Its use should be explicitly controlled by the consumer.

Describe alternatives you've considered

A configurable automatic conversion to associative arrays would preserve existing behavior, but introduce application-specific conversion logic and additional maintenance overhead into the SDK's argument-handling pipeline.

Existing Composer packages also provide object-to-array conversion, so consumers could handle this independently without additional SDK functionality.

Additional context

Related to #586, which addresses the loss of JSON type information during decoding and its impact on schema validation.

This request concerns the subsequent delivery of validated values to tool handlers.

The change would be breaking for consumers expecting associative arrays, but could be introduced before the SDK reaches 1.0. Preserving the current interface merely for convenience or backward compatibility would be an unfortunate design decision, as it would perpetuate unnecessary coupling to a specific PHP representation instead of establishing a clean, type-preserving API.