fix Prompt type gaps with 2025-06-18 spec

[topherbullock]

Motivation and Context

add title field to prompt argument 701f6fa

PromptArgument extends BaseMetadata, which includes both name and
title

• https://github.com/modelcontextprotocol/modelcontextprotocol/blob/51e093b8ebfde5e968879024566b7380d30c52d0/schema/2025-06-18/schema.ts#L686-L698
• https://github.com/modelcontextprotocol/modelcontextprotocol/blob/51e093b8ebfde5e968879024566b7380d30c52d0/schema/2025-06-18/schema.ts#L294-l309

add _meta field to Prompt 390e6b8

See General fields: _meta for notes on _meta usage.

https://github.com/modelcontextprotocol/modelcontextprotocol/blob/51e093b8ebfde5e968879024566b7380d30c52d0/schema/2025-06-18/schema.ts#L680-L683

How Has This Been Tested?

updated existing tests for prompt construction to include meta field and argument titles.

Breaking Changes

None

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

simplifying sharing BaseMetadata behaviour with a module mixin' coming in follow up PR - wip ; e2a8f27

[koic]

It seems that the tests passes even without safe navigation. Is it necessary?

Suggested change

	arguments: arguments_value&.map(&:to_h),
	arguments: arguments_value.map(&:to_h),

[topherbullock]

good callout - this is a possible state if a Prompt class doesn't define arguments.

I added a test to exercise and cover this behaviour.

ruby-sdk/test/mcp/prompt_test.rb

Lines 180 to 193 in a1dd3dd

	test "#to_h handles nil arguments value" do
	class NoArgumentsPrompt < Prompt
	description "No arguments prompt"
	end
	prompt = NoArgumentsPrompt
	expected = {
	name: "no_arguments_prompt",
	description: "No arguments prompt",
	}
	assert_equal expected, prompt.to_h
	end
	end