Nicer returns

Author: afstanton

lib/tool_forge.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require 'json'
 require 'zeitwerk'
 
 loader = Zeitwerk::Loader.for_gem(warn_on_extra_files: false)

lib/tool_forge/tool_definition.rb

@@ -84,7 +84,18 @@ def to_mcp_tool
 
         define_singleton_method(:call) do |server_context:, **args|
           result = definition.execute_block.call(**args)
-          MCP::Tool::Response.new([{ type: 'text', text: result.to_s }])
+
+          # Smart formatting for different return types
+          result_text = case result
+                        when String
+                          result
+                        when Hash, Array
+                          JSON.pretty_generate(result)
+                        else
+                          result.to_s
+                        end
+
+          MCP::Tool::Response.new([{ type: 'text', text: result_text }])
         end
       end
     end

spec/tool_forge/tool_definition_to_mcp_spec.rb

@@ -134,4 +134,52 @@
     expect(schema[:properties]['arr'][:type]).to eq('array')
     expect(schema[:properties]['obj'][:type]).to eq('object')
   end
+
+  describe 'return value formatting' do
+    it 'returns strings as-is' do
+      tool = described_class.new(:string_tool) do
+        description 'Returns a string'
+        execute { 'Hello, World!' }
+      end
+
+      tool_class = tool.to_mcp_tool
+      result = tool_class.call(server_context: nil)
+      expect(result.content.first[:text]).to eq('Hello, World!')
+    end
+
+    it 'formats hashes as pretty JSON' do
+      tool = described_class.new(:hash_tool) do
+        description 'Returns a hash'
+        execute { { name: 'Alice', age: 30 } }
+      end
+
+      tool_class = tool.to_mcp_tool
+      result = tool_class.call(server_context: nil)
+      parsed = JSON.parse(result.content.first[:text])
+      expect(parsed).to eq('name' => 'Alice', 'age' => 30)
+    end
+
+    it 'formats arrays as pretty JSON' do
+      tool = described_class.new(:array_tool) do
+        description 'Returns an array'
+        execute { [1, 2, 3, 4, 5] }
+      end
+
+      tool_class = tool.to_mcp_tool
+      result = tool_class.call(server_context: nil)
+      parsed = JSON.parse(result.content.first[:text])
+      expect(parsed).to eq([1, 2, 3, 4, 5])
+    end
+
+    it 'converts other objects to strings' do
+      tool = described_class.new(:number_tool) do
+        description 'Returns a number'
+        execute { 42 }
+      end
+
+      tool_class = tool.to_mcp_tool
+      result = tool_class.call(server_context: nil)
+      expect(result.content.first[:text]).to eq('42')
+    end
+  end
 end