Add Tool output_schema support with comprehensive validation
This commit implements optional JSON Schema validation for tool outputs according to the MCP specification: - Add MCP::Tool::OutputSchema class mirroring InputSchema functionality - Support output_schema in class definitions, Tool.define, and OutputSchema objects - Include validate_result method for runtime validation - Update MCP::Client::Tool to track output schemas - Add comprehensive test coverage with 249 passing tests - Update README with dedicated Tool Output Schemas section - Follow MCP spec requirements for server/client validation
This commit is contained in:
Valentino Stoll
parent
3f2a4b3b21
commit
aad8e94530
3 changed files with 495 additions and 7 deletions
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@ -28,6 +28,38 @@ module MCP
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@tool.input_schema,
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)
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end
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def test_output_schema_returns_nil_when_not_provided
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assert_nil(@tool.output_schema)
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end
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def test_output_schema_returns_output_schema_when_provided
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tool_with_output = Tool.new(
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name: "test_tool_with_output",
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description: "A test tool with output schema",
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input_schema: { "type" => "object", "properties" => { "foo" => { "type" => "string" } } },
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output_schema: { "type" => "object", "properties" => { "result" => { "type" => "string" } } },
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)
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assert_equal(
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{ "type" => "object", "properties" => { "result" => { "type" => "string" } } },
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tool_with_output.output_schema,
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)
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end
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def test_initialization_with_all_parameters
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tool = Tool.new(
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name: "full_tool",
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description: "A tool with all parameters",
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input_schema: { "type" => "object" },
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output_schema: { "type" => "object", "properties" => { "status" => { "type" => "boolean" } } },
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)
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assert_equal("full_tool", tool.name)
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assert_equal("A tool with all parameters", tool.description)
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assert_equal({ "type" => "object" }, tool.input_schema)
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assert_equal({ "type" => "object", "properties" => { "status" => { "type" => "boolean" } } }, tool.output_schema)
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end
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end
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end
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end
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140
test/mcp/tool/output_schema_test.rb
Normal file
140
test/mcp/tool/output_schema_test.rb
Normal file
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@ -0,0 +1,140 @@
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# frozen_string_literal: true
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require "test_helper"
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module MCP
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class Tool
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class OutputSchemaTest < ActiveSupport::TestCase
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test "required arguments are converted to symbols" do
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output_schema = OutputSchema.new(properties: { result: { type: "string" } }, required: ["result"])
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assert_equal [:result], output_schema.required
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end
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test "to_h returns a hash representation of the output schema" do
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output_schema = OutputSchema.new(properties: { result: { type: "string" } }, required: [:result])
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assert_equal(
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{ type: "object", properties: { result: { type: "string" } }, required: [:result] },
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output_schema.to_h,
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)
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end
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test "validate_result validates result against the schema" do
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output_schema = OutputSchema.new(properties: { result: { type: "string" } }, required: [:result])
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assert_nothing_raised do
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output_schema.validate_result({ result: "success" })
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end
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end
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test "validate_result raises error for invalid result" do
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output_schema = OutputSchema.new(properties: { result: { type: "string" } }, required: [:result])
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assert_raises(OutputSchema::ValidationError) do
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output_schema.validate_result({ result: 123 })
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end
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end
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test "validate_result raises error for missing required field" do
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output_schema = OutputSchema.new(properties: { result: { type: "string" } }, required: [:result])
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assert_raises(OutputSchema::ValidationError) do
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output_schema.validate_result({})
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end
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end
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test "valid schema initialization" do
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schema = OutputSchema.new(properties: { foo: { type: "string" } }, required: [:foo])
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assert_equal({ type: "object", properties: { foo: { type: "string" } }, required: [:foo] }, schema.to_h)
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end
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test "invalid schema raises argument error" do
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assert_raises(ArgumentError) do
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OutputSchema.new(properties: { foo: { type: "invalid_type" } }, required: [:foo])
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end
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end
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test "schema without required arguments is valid" do
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assert_nothing_raised do
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OutputSchema.new(properties: { foo: { type: "string" } })
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end
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end
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test "unexpected errors bubble up from validate_result" do
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schema = OutputSchema.new(properties: { foo: { type: "string" } }, required: [:foo])
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JSON::Validator.stub(:fully_validate, ->(*) { raise "unexpected error" }) do
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assert_raises(RuntimeError) do
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schema.validate_result({ foo: "bar" })
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end
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end
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end
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test "rejects schemas with $ref references" do
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assert_raises(ArgumentError) do
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OutputSchema.new(properties: { foo: { "$ref" => "#/definitions/bar" } }, required: [:foo])
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end
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end
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test "rejects schemas with symbol $ref references" do
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assert_raises(ArgumentError) do
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OutputSchema.new(properties: { foo: { :$ref => "#/definitions/bar" } }, required: [:foo])
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end
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end
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test "== compares two output schemas with the same properties and required fields" do
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schema1 = OutputSchema.new(properties: { foo: { type: "string" } }, required: [:foo])
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schema2 = OutputSchema.new(properties: { foo: { type: "string" } }, required: [:foo])
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assert_equal schema1, schema2
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schema3 = OutputSchema.new(properties: { bar: { type: "string" } }, required: [:bar])
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refute_equal schema1, schema3
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schema4 = OutputSchema.new(properties: { foo: { type: "string" } }, required: [:bar])
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refute_equal schema1, schema4
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schema5 = OutputSchema.new(properties: { bar: { type: "string" } }, required: [:foo])
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refute_equal schema1, schema5
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end
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test "empty schema is valid" do
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schema = OutputSchema.new
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assert_equal({ type: "object" }, schema.to_h)
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end
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test "validates complex nested schemas" do
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schema = OutputSchema.new(
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properties: {
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data: {
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type: "object",
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properties: {
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items: { type: "array", items: { type: "string" } },
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count: { type: "integer", minimum: 0 },
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},
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required: ["items"],
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},
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},
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required: [:data],
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)
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valid_result = {
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data: {
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items: ["item1", "item2"],
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count: 2,
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},
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}
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assert_nothing_raised do
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schema.validate_result(valid_result)
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end
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invalid_result = {
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data: {
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items: [123, 456], # Should be strings
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count: 2,
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},
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}
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assert_raises(OutputSchema::ValidationError) do
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schema.validate_result(invalid_result)
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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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@ -255,5 +255,133 @@ module MCP
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end
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assert_match(/Invalid JSON Schema/, error.message)
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end
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test "#to_h includes outputSchema when present" do
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tool = Tool.define(
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name: "mock_tool",
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title: "Mock Tool",
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description: "a mock tool for testing",
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output_schema: { properties: { result: { type: "string" } }, required: ["result"] },
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)
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expected = {
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name: "mock_tool",
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title: "Mock Tool",
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description: "a mock tool for testing",
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inputSchema: { type: "object" },
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outputSchema: { type: "object", properties: { result: { type: "string" } }, required: [:result] },
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}
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assert_equal expected, tool.to_h
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end
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test "#to_h does not include outputSchema when not set" do
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tool = Tool.define(
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name: "mock_tool",
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description: "a mock tool for testing",
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)
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refute tool.to_h.key?(:outputSchema)
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end
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test "output_schema defaults to nil" do
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class NoOutputSchemaTool < Tool; end
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tool = NoOutputSchemaTool
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assert_nil tool.output_schema
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end
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test "accepts output_schema as a hash" do
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class HashOutputSchemaTool < Tool
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output_schema({ properties: { result: { type: "string" } }, required: [:result] })
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end
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tool = HashOutputSchemaTool
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expected = { type: "object", properties: { result: { type: "string" } }, required: [:result] }
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assert_equal expected, tool.output_schema.to_h
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end
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test "accepts output_schema as an OutputSchema object" do
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class OutputSchemaObjectTool < Tool
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output_schema Tool::OutputSchema.new(properties: { result: { type: "string" } }, required: [:result])
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end
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tool = OutputSchemaObjectTool
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expected = { type: "object", properties: { result: { type: "string" } }, required: [:result] }
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assert_equal expected, tool.output_schema.to_h
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end
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test "output_schema raises detailed error message for invalid schema" do
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error = assert_raises(ArgumentError) do
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Class.new(MCP::Tool) do
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output_schema(
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properties: {
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count: { type: "integer", minimum: "not a number" },
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},
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required: [:count],
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)
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end
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end
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assert_includes error.message, "Invalid JSON Schema"
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assert_includes error.message, "#/properties/count/minimum"
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assert_includes error.message, "string did not match the following type: number"
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end
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test "output_schema rejects any $ref in schema" do
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schema_with_ref = {
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properties: {
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foo: { "$ref" => "#/definitions/bar" },
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},
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required: ["foo"],
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definitions: {
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bar: { type: "string" },
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},
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}
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error = assert_raises(ArgumentError) do
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Class.new(MCP::Tool) do
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output_schema schema_with_ref
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end
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end
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assert_match(/Invalid JSON Schema/, error.message)
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end
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test ".define allows definition of tools with output_schema" do
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tool = Tool.define(
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name: "mock_tool",
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title: "Mock Tool",
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description: "a mock tool for testing",
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output_schema: { properties: { result: { type: "string" } }, required: ["result"] },
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) do |_|
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Tool::Response.new([{ type: "text", content: "OK" }])
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end
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assert_equal "mock_tool", tool.name_value
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assert_equal "a mock tool for testing", tool.description
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assert_instance_of Tool::OutputSchema, tool.output_schema
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expected_output_schema = { type: "object", properties: { result: { type: "string" } }, required: [:result] }
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assert_equal expected_output_schema, tool.output_schema.to_h
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end
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class TestToolWithOutputSchema < Tool
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tool_name "test_tool_with_output"
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description "a test tool with output schema"
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input_schema({ properties: { message: { type: "string" } }, required: ["message"] })
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output_schema({ properties: { result: { type: "string" }, success: { type: "boolean" } }, required: ["result", "success"] })
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class << self
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def call(message:, server_context: nil)
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Tool::Response.new([{ type: "text", content: "OK" }])
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end
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end
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end
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test "declarative definition of tools with output schema" do
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tool = TestToolWithOutputSchema
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assert_equal "test_tool_with_output", tool.name_value
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assert_equal "a test tool with output schema", tool.description
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expected_input = { type: "object", properties: { message: { type: "string" } }, required: [:message] }
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assert_equal expected_input, tool.input_schema.to_h
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expected_output = { type: "object", properties: { result: { type: "string" }, success: { type: "boolean" } }, required: [:result, :success] }
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assert_equal expected_output, tool.output_schema.to_h
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end
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end
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end
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