diff --git a/pydantic_ai_slim/pydantic_ai/_output.py b/pydantic_ai_slim/pydantic_ai/_output.py
index 916ddb7e83..dc41a4a50d 100644
--- a/pydantic_ai_slim/pydantic_ai/_output.py
+++ b/pydantic_ai_slim/pydantic_ai/_output.py
@@ -211,9 +211,13 @@ def build(
                 tool_output_type = output_type
 
             if tool_name is None:
-                tool_name = default_tool_name
-                if multiple:
-                    tool_name += f'_{tool_output_type.__name__}'
+                tool_name = (
+                    tool_output_type.__name__
+                    if inspect.isfunction(tool_output_type)
+                    else f'{default_tool_name}_{tool_output_type.__name__}'
+                    if multiple
+                    else default_tool_name
+                )
 
             i = 1
             original_tool_name = tool_name
diff --git a/tests/test_agent.py b/tests/test_agent.py
index d598481551..5cb5b725a9 100644
--- a/tests/test_agent.py
+++ b/tests/test_agent.py
@@ -632,7 +632,7 @@ def call_tool(_: list[ModelMessage], info: AgentInfo) -> ModelResponse:
     assert output_tools == snapshot(
         [
             ToolDefinition(
-                name='final_result',
+                name='get_weather',
                 description='The final response which ends this conversation',
                 parameters_json_schema={
                     'additionalProperties': False,
@@ -671,7 +671,7 @@ def call_tool(_: list[ModelMessage], info: AgentInfo) -> ModelResponse:
     assert output_tools == snapshot(
         [
             ToolDefinition(
-                name='final_result',
+                name='get_weather',
                 description='The final response which ends this conversation',
                 parameters_json_schema={
                     'additionalProperties': False,
@@ -801,7 +801,7 @@ def call_tool(messages: list[ModelMessage], info: AgentInfo) -> ModelResponse:
             ModelResponse(
                 parts=[
                     ToolCallPart(
-                        tool_name='final_result',
+                        tool_name='get_weather',
                         args='{"city": "New York City"}',
                         tool_call_id=IsStr(),
                     )
@@ -814,7 +814,7 @@ def call_tool(messages: list[ModelMessage], info: AgentInfo) -> ModelResponse:
                 parts=[
                     RetryPromptPart(
                         content='City not found, I only know Mexico City',
-                        tool_name='final_result',
+                        tool_name='get_weather',
                         tool_call_id=IsStr(),
                         timestamp=IsDatetime(),
                     )
@@ -823,7 +823,7 @@ def call_tool(messages: list[ModelMessage], info: AgentInfo) -> ModelResponse:
             ModelResponse(
                 parts=[
                     ToolCallPart(
-                        tool_name='final_result',
+                        tool_name='get_weather',
                         args='{"city": "Mexico City"}',
                         tool_call_id=IsStr(),
                     )
@@ -835,7 +835,7 @@ def call_tool(messages: list[ModelMessage], info: AgentInfo) -> ModelResponse:
             ModelRequest(
                 parts=[
                     ToolReturnPart(
-                        tool_name='final_result',
+                        tool_name='get_weather',
                         content='Final result processed.',
                         tool_call_id=IsStr(),
                         timestamp=IsDatetime(),
@@ -871,7 +871,7 @@ def call_tool(_: list[ModelMessage], info: AgentInfo) -> ModelResponse:
     assert output_tools == snapshot(
         [
             ToolDefinition(
-                name='final_result',
+                name='get_weather',
                 description='The final response which ends this conversation',
                 parameters_json_schema={
                     'additionalProperties': False,
@@ -947,7 +947,7 @@ def call_tool(_: list[ModelMessage], info: AgentInfo) -> ModelResponse:
     assert output_tools == snapshot(
         [
             ToolDefinition(
-                name='final_result_get_weather',
+                name='get_weather',
                 description='get_weather: The final response which ends this conversation',
                 parameters_json_schema={
                     'additionalProperties': False,
@@ -1017,7 +1017,7 @@ def call_handoff_tool(messages: list[ModelMessage], info: AgentInfo) -> ModelRes
             ModelResponse(
                 parts=[
                     ToolCallPart(
-                        tool_name='final_result',
+                        tool_name='handoff',
                         args='{"city": "Mexico City"}',
                         tool_call_id=IsStr(),
                     )
@@ -1029,7 +1029,7 @@ def call_handoff_tool(messages: list[ModelMessage], info: AgentInfo) -> ModelRes
             ModelRequest(
                 parts=[
                     ToolReturnPart(
-                        tool_name='final_result',
+                        tool_name='handoff',
                         content='Final result processed.',
                         tool_call_id=IsStr(),
                         timestamp=IsDatetime(),
@@ -1052,7 +1052,7 @@ def call_handoff_tool(messages: list[ModelMessage], info: AgentInfo) -> ModelRes
             ModelResponse(
                 parts=[
                     ToolCallPart(
-                        tool_name='final_result',
+                        tool_name='get_weather',
                         args='{"city": "Mexico City"}',
                         tool_call_id=IsStr(),
                     )
@@ -1064,7 +1064,7 @@ def call_handoff_tool(messages: list[ModelMessage], info: AgentInfo) -> ModelRes
             ModelRequest(
                 parts=[
                     ToolReturnPart(
-                        tool_name='final_result',
+                        tool_name='get_weather',
                         content='Final result processed.',
                         tool_call_id=IsStr(),
                         timestamp=IsDatetime(),
diff --git a/tests/test_examples.py b/tests/test_examples.py
index ad377bedbf..5bef09b30d 100644
--- a/tests/test_examples.py
+++ b/tests/test_examples.py
@@ -406,23 +406,23 @@ async def list_tools() -> list[None]:
         tool_call_id='pyd_ai_2e0e396768a14fe482df90a29a78dc7b',
     ),
     'Select the names and countries of all capitals': ToolCallPart(
-        tool_name='final_result_hand_off_to_sql_agent',
+        tool_name='hand_off_to_sql_agent',
         args={'query': 'SELECT name, country FROM capitals;'},
     ),
     'SELECT name, country FROM capitals;': ToolCallPart(
-        tool_name='final_result_run_sql_query',
+        tool_name='run_sql_query',
         args={'query': 'SELECT name, country FROM capitals;'},
     ),
     'SELECT * FROM capital_cities;': ToolCallPart(
-        tool_name='final_result_run_sql_query',
+        tool_name='run_sql_query',
         args={'query': 'SELECT * FROM capital_cities;'},
     ),
     'Select all pets': ToolCallPart(
-        tool_name='final_result_hand_off_to_sql_agent',
+        tool_name='hand_off_to_sql_agent',
         args={'query': 'SELECT * FROM pets;'},
     ),
     'SELECT * FROM pets;': ToolCallPart(
-        tool_name='final_result_run_sql_query',
+        tool_name='run_sql_query',
         args={'query': 'SELECT * FROM pets;'},
     ),
     'How do I fly from Amsterdam to Mexico City?': ToolCallPart(
@@ -614,13 +614,13 @@ async def model_logic(  # noqa: C901
         )
     elif (
         isinstance(m, RetryPromptPart)
-        and m.tool_name == 'final_result_run_sql_query'
+        and m.tool_name == 'run_sql_query'
         and m.content == "Only 'SELECT *' is supported, you'll have to do column filtering manually."
     ):
         return ModelResponse(
             parts=[
                 ToolCallPart(
-                    tool_name='final_result_run_sql_query',
+                    tool_name='run_sql_query',
                     args={'query': 'SELECT * FROM capitals;'},
                     tool_call_id='pyd_ai_tool_call_id',
                 )
@@ -628,14 +628,14 @@ async def model_logic(  # noqa: C901
         )
     elif (
         isinstance(m, RetryPromptPart)
-        and m.tool_name == 'final_result_hand_off_to_sql_agent'
+        and m.tool_name == 'hand_off_to_sql_agent'
         and m.content
         == "SQL agent failed: Unknown table 'capitals' in query 'SELECT * FROM capitals;'. Available tables: capital_cities."
     ):
         return ModelResponse(
             parts=[
                 ToolCallPart(
-                    tool_name='final_result_hand_off_to_sql_agent',
+                    tool_name='hand_off_to_sql_agent',
                     args={'query': 'SELECT * FROM capital_cities;'},
                     tool_call_id='pyd_ai_tool_call_id',
                 )
@@ -643,7 +643,7 @@ async def model_logic(  # noqa: C901
         )
     elif (
         isinstance(m, RetryPromptPart)
-        and m.tool_name == 'final_result_run_sql_query'
+        and m.tool_name == 'run_sql_query'
         and m.content == "Unknown table 'pets' in query 'SELECT * FROM pets;'. Available tables: capital_cities."
     ):
         return ModelResponse(
@@ -660,7 +660,7 @@ async def model_logic(  # noqa: C901
     # SQL agent failed: The table 'pets' does not exist in the database. Only the table 'capital_cities' is available.
     elif (
         isinstance(m, RetryPromptPart)
-        and m.tool_name == 'final_result_hand_off_to_sql_agent'
+        and m.tool_name == 'hand_off_to_sql_agent'
         and m.content
         == "SQL agent failed: The table 'pets' does not exist in the database. Only the table 'capital_cities' is available."
     ):