Expose server tool annotations on MCP::Client::Tool

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Expose the server's `annotations` field on `MCP::Client::Tool` — `Client#tools`/`#list_tools` previously dropped it
+
 ## [0.23.0] - 2026-07-07
 
 ### Added

lib/mcp/client.rb

@@ -131,6 +131,7 @@ def list_tools(cursor: nil, meta: nil, cancellation: nil)
           description: tool["description"],
           input_schema: tool["inputSchema"],
           output_schema: tool["outputSchema"],
+          annotations: tool["annotations"],
         )
       end
 

lib/mcp/client/tool.rb

@@ -3,13 +3,14 @@
 module MCP
   class Client
     class Tool
-      attr_reader :name, :description, :input_schema, :output_schema
+      attr_reader :name, :description, :input_schema, :output_schema, :annotations
 
-      def initialize(name:, description:, input_schema:, output_schema: nil)
+      def initialize(name:, description:, input_schema:, output_schema: nil, annotations: nil)
         @name = name
         @description = description
         @input_schema = input_schema
         @output_schema = output_schema
+        @annotations = annotations
       end
     end
   end

test/mcp/client/tool_test.rb

@@ -33,6 +33,24 @@ def test_output_schema_returns_nil_when_not_provided
         assert_nil(@tool.output_schema)
       end
 
+      def test_annotations_returns_nil_when_not_provided
+        assert_nil(@tool.annotations)
+      end
+
+      def test_annotations_returns_annotations_when_provided
+        tool_with_annotations = Tool.new(
+          name: "test_tool_with_annotations",
+          description: "A test tool with annotations",
+          input_schema: { "type" => "object" },
+          annotations: { "readOnlyHint" => true, "title" => "Test Tool" },
+        )
+
+        assert_equal(
+          { "readOnlyHint" => true, "title" => "Test Tool" },
+          tool_with_annotations.annotations,
+        )
+      end
+
       def test_output_schema_returns_output_schema_when_provided
         tool_with_output = Tool.new(
           name: "test_tool_with_output",
@@ -53,12 +71,14 @@ def test_initialization_with_all_parameters
           description: "A tool with all parameters",
           input_schema: { "type" => "object" },
           output_schema: { "type" => "object", "properties" => { "status" => { "type" => "boolean" } } },
+          annotations: { "readOnlyHint" => true },
         )
 
         assert_equal("full_tool", tool.name)
         assert_equal("A tool with all parameters", tool.description)
         assert_equal({ "type" => "object" }, tool.input_schema)
         assert_equal({ "type" => "object", "properties" => { "status" => { "type" => "boolean" } } }, tool.output_schema)
+        assert_equal({ "readOnlyHint" => true }, tool.annotations)
       end
     end
   end

test/mcp/client_test.rb

@@ -86,6 +86,7 @@ def test_tools_sends_request_to_transport_and_returns_tools_array
               "description" => "tool1",
               "inputSchema" => {},
               "outputSchema" => { "type" => "object", "properties" => { "result" => { "type" => "string" } } },
+              "annotations" => { "readOnlyHint" => true, "title" => "Tool One" },
             },
             { "name" => "tool2", "description" => "tool2", "inputSchema" => {} },
           ],
@@ -103,8 +104,10 @@ def test_tools_sends_request_to_transport_and_returns_tools_array
       assert_equal(2, tools.size)
       assert_equal("tool1", tools.first.name)
       assert_equal({ "type" => "object", "properties" => { "result" => { "type" => "string" } } }, tools.first.output_schema)
+      assert_equal({ "readOnlyHint" => true, "title" => "Tool One" }, tools.first.annotations)
       assert_equal("tool2", tools.last.name)
       assert_nil(tools.last.output_schema)
+      assert_nil(tools.last.annotations)
     end
 
     def test_tools_returns_empty_array_when_no_tools