diff --git a/docs/_core_features/tools.md b/docs/_core_features/tools.md
index b8c9d1388..b138c2b7d 100644
--- a/docs/_core_features/tools.md
+++ b/docs/_core_features/tools.md
@@ -85,6 +85,15 @@ end
 > ```
 {: .note }
 
+> If a model attempts to call a tool that doesn't exist (sometimes called "tool hallucination"), RubyLLM handles this gracefully by:
+>
+> 1. Returning an error message to the model indicating which tool it tried to call
+> 2. Listing the actually available tools
+> 3. Allowing the conversation to continue so the model can correct itself
+>
+> This prevents crashes and gives the model a chance to use the correct tool or respond appropriately.
+{: .note }
+
 ## Declaring Parameters
 
 RubyLLM ships with two complementary approaches:
diff --git a/lib/ruby_llm/chat.rb b/lib/ruby_llm/chat.rb
index bf35ed5eb..3fe6c2213 100644
--- a/lib/ruby_llm/chat.rb
+++ b/lib/ruby_llm/chat.rb
@@ -209,6 +209,13 @@ def handle_tool_calls(response, &) # rubocop:disable Metrics/PerceivedComplexity
 
     def execute_tool(tool_call)
       tool = tools[tool_call.name.to_sym]
+      if tool.nil?
+        return {
+          error: "Model tried to call unavailable tool `#{tool_call.name}`. " \
+                 "Available tools: #{tools.keys.to_json}."
+        }
+      end
+
       args = tool_call.arguments
       tool.call(args)
     end
diff --git a/spec/ruby_llm/chat_tools_spec.rb b/spec/ruby_llm/chat_tools_spec.rb
index 385cef2bb..de6abb9f9 100644
--- a/spec/ruby_llm/chat_tools_spec.rb
+++ b/spec/ruby_llm/chat_tools_spec.rb
@@ -171,6 +171,40 @@ def tool_result_message_for(chat, tool_call)
         expect(response.content).to include('15')
         expect(response.content).to include('10')
       end
+
+      it "#{provider}/#{model} deals with non-existent tool calls" do
+        hallucinated_tool_call = RubyLLM::ToolCall.new(
+          id: 'call_1',
+          name: 'list_tools',
+          arguments: {}
+        )
+
+        tool_results_received = []
+
+        chat = RubyLLM.chat(model: model, provider: provider)
+                      .with_tool(Weather)
+                      .on_tool_result { |result| tool_results_received << result }
+
+        final_answer = 'The `list_tools` tool is not supported, but I see you have the `weather` tool.'
+        allow(chat.instance_variable_get(:@provider)).to receive(:complete).and_return(
+          RubyLLM::Message.new(
+            role: :assistant,
+            content: '',
+            tool_calls: { hallucinated_tool_call.id => hallucinated_tool_call }
+          ),
+          RubyLLM::Message.new(
+            role: :assistant,
+            content: final_answer
+          )
+        )
+
+        response = chat.ask('What tools do you support?')
+        expect(response.content).to eq(final_answer)
+        expect(tool_results_received).to eq([
+                                              { error: 'Model tried to call unavailable tool `list_tools`. ' \
+                                                       'Available tools: ["weather"].' }
+                                            ])
+      end
     end
 
     describe 'thought signatures' do