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Fix missing output_schema argument in 'define_tool' API #301

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Fix missing output_schema argument in 'define_tool' API #301

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4 changes: 2 additions & 2 deletions lib/mcp/server.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -145,8 +145,8 @@ def handle_json(request, session: nil)
end
end

def define_tool(name: nil, title: nil, description: nil, input_schema: nil, annotations: nil, meta: nil, &block)
tool = Tool.define(name: name, title: title, description: description, input_schema: input_schema, annotations: annotations, meta: meta, &block)
def define_tool(name: nil, title: nil, description: nil, input_schema: nil, output_schema: nil, annotations: nil, meta: nil, &block)
tool = Tool.define(name: name, title: title, description: description, input_schema: input_schema, output_schema: output_schema, annotations: annotations, meta: meta, &block)
tool_name = tool.name_value

@tool_names << tool_name
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9 changes: 7 additions & 2 deletions test/mcp/server_test.rb
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Expand Up @@ -1127,19 +1127,24 @@ class Example < Tool
name: "defined_tool",
description: "Defined tool",
input_schema: { type: "object", properties: { message: { type: "string" } }, required: ["message"] },
output_schema: { type: "object", properties: { response: { type: "string" } }, required: ["response"] },
meta: { foo: "bar" },
) do |message:|
Tool::Response.new(message)
Tool::Response.new({ "response" => message })
end

stored_tool = @server.instance_variable_get(:@tools)["defined_tool"]
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@koic koic Apr 7, 2026

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Suggested change
stored_tool = @server.instance_variable_get(:@tools)["defined_tool"]
stored_tool = @server.tools["defined_tool"]

assert_not_nil(stored_tool)
assert_equal(MCP::Tool::OutputSchema.new({ type: "object", properties: { response: { type: "string" } }, required: ["response"] }), stored_tool.output_schema)

response = @server.handle({
jsonrpc: "2.0",
method: "tools/call",
params: { name: "defined_tool", arguments: { message: "success" } },
id: 1,
})

assert_equal({ content: "success", isError: false }, response[:result])
assert_equal({ content: { "response" => "success" }, isError: false }, response[:result])
end

test "#define_tool adds a tool with duplicated tool name to the server" do
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