Replace custom `deep_transform_keys` in `Tool::Schema` and
string key access in `StreamableHTTPTransport` with
the `symbolize_names: true` option of `JSON.parse`.
This aligns `StreamableHTTPTransport` with `StdioTransport`,
which already uses `symbolize_names: true`.
This refactoring extracts common schema validation logic into a base Schema
class, eliminating ~100 lines of duplicate code between InputSchema and
OutputSchema. It also adds support for the JSON Schema `additionalProperties`
keyword to allow fine-grained control over extra properties in tool arguments.
Previously `additionalParameters` could be set only on OutputSchema.
Key changes:
- Created MCP::Tool::Schema base class consolidating:
- Schema validation against JSON Schema Draft 4 metaschema
- Deep key transformation (string to symbol conversion)
- $ref disallowance checking
- Common validation methods
- Refactored InputSchema to inherit from Schema:
- Simplified constructor to accept full schema hash
- Changed required fields storage from symbols to strings
- Removed ~40 lines of duplicated validation logic
- Refactored OutputSchema to inherit from Schema:
- Removed ~54 lines of duplicated validation logic
- Now shares all common functionality with InputSchema
- Updated Tool.input_schema setter:
- Simplified to pass full hash directly to InputSchema
- Added additionalProperties support:
- By default, tools now allow additional properties (JSON Schema default)
- Can explicitly set `additionalProperties: false` to disallow extras
- Added comprehensive test coverage for both behaviors
