99cbefc610
`Tool::Schema` rejected `$ref` with an `ArgumentError`. Earlier MCP spec versions (2024-11-05 through 2025-06-18) did not define a JSON Schema dialect or reference the `$ref` keyword. `inputSchema` was described only as "JSON Schema defining expected parameters" with no further constraints: - https://modelcontextprotocol.io/specification/2024-11-05/server/tools - https://modelcontextprotocol.io/specification/2025-06-18/server/tools The MCP spec 2025-11-25 introduced a "JSON Schema Usage" section that adopts JSON Schema 2020-12 as the default dialect. Since `$ref` is a core keyword in 2020-12, it is now allowed for protocol version 2025-11-25 and later. - https://modelcontextprotocol.io/specification/2025-11-25/basic#json-schema-usage - https://modelcontextprotocol.io/specification/2025-11-25/server/tools - https://json-schema.org/draft/2020-12/release-notes For backward compatibility with older protocol versions (2025-06-18 and earlier), `Server#validate!` continues to raise `ArgumentError` when a tool input schema contains `$ref`. This preserves the existing behavior for servers targeting those spec versions.
61 lines
1.7 KiB
Ruby
61 lines
1.7 KiB
Ruby
# frozen_string_literal: true
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require "json-schema"
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module MCP
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class Tool
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class Schema
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attr_reader :schema
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def initialize(schema = {})
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@schema = deep_transform_keys(JSON.parse(JSON.dump(schema)), &:to_sym)
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@schema[:type] ||= "object"
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validate_schema!
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end
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def ==(other)
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other.is_a?(self.class) && schema == other.schema
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end
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def to_h
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@schema
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end
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private
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def fully_validate(data)
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JSON::Validator.fully_validate(to_h, data)
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end
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def deep_transform_keys(schema, &block)
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case schema
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when Hash
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schema.each_with_object({}) do |(key, value), result|
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result[yield(key)] = deep_transform_keys(value, &block)
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end
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when Array
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schema.map { |e| deep_transform_keys(e, &block) }
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else
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schema
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end
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end
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def validate_schema!
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schema = to_h
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gem_path = File.realpath(Gem.loaded_specs["json-schema"].full_gem_path)
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schema_reader = JSON::Schema::Reader.new(
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accept_uri: false,
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accept_file: ->(path) { File.realpath(path.to_s).start_with?(gem_path) },
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)
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metaschema_path = Pathname.new(JSON::Validator.validator_for_name("draft4").metaschema)
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# Converts metaschema to a file URI for cross-platform compatibility
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metaschema_uri = JSON::Util::URI.file_uri(metaschema_path.expand_path.cleanpath.to_s.tr("\\", "/"))
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metaschema = metaschema_uri.to_s
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errors = JSON::Validator.fully_validate(metaschema, schema, schema_reader: schema_reader)
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if errors.any?
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raise ArgumentError, "Invalid JSON Schema: #{errors.join(", ")}"
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end
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end
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end
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end
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end
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