feat: add native OpenTelemetry agentic metrics

New metrics added:
- gen_ai.agent.invocation.duration
- gen_ai.tool.execution.duration
- gen_ai.agent.request.size
- gen_ai.agent.response.size
- gen_ai.agent.workflow.steps

New metrics and attributes are in line with OTel semantic conventions where possible, and will be formally to the semconv later.

PiperOrigin-RevId: 901223911

Author: google-genai-bot

src/google/adk/agents/base_agent.py

@@ -42,7 +42,8 @@
 from ..events.event_actions import EventActions
 from ..features import experimental
 from ..features import FeatureName
-from ..telemetry import _instrumentation
+from ..telemetry import tracing
+from ..telemetry.tracing import tracer
 from ..utils.context_utils import Aclosing
 from .base_agent_config import BaseAgentConfig
 from .callback_context import CallbackContext
@@ -284,8 +285,9 @@ async def run_async(
       Event: the events generated by the agent.
     """
 
-    ctx = self._create_invocation_context(parent_context)
-    async with _instrumentation.record_agent_invocation(ctx, self):
+    with tracer.start_as_current_span(f'invoke_agent {self.name}') as span:
+      ctx = self._create_invocation_context(parent_context)
+      tracing.trace_agent_invocation(span, self, ctx)
       if event := await self._handle_before_agent_callback(ctx):
         yield event
       if ctx.end_invocation:
@@ -316,8 +318,9 @@ async def run_live(
       Event: the events generated by the agent.
     """
 
-    ctx = self._create_invocation_context(parent_context)
-    async with _instrumentation.record_agent_invocation(ctx, self):
+    with tracer.start_as_current_span(f'invoke_agent {self.name}') as span:
+      ctx = self._create_invocation_context(parent_context)
+      tracing.trace_agent_invocation(span, self, ctx)
       if event := await self._handle_before_agent_callback(ctx):
         yield event
       if ctx.end_invocation:

src/google/adk/flows/llm_flows/functions.py

@@ -22,6 +22,7 @@
 from concurrent.futures import ThreadPoolExecutor
 import contextvars
 import copy
+import functools
 import inspect
 import logging
 import threading
@@ -42,8 +43,8 @@
 from ...auth.auth_tool import AuthToolArguments
 from ...events.event import Event
 from ...events.event_actions import EventActions
-from ...telemetry import _instrumentation
 from ...telemetry.tracing import trace_merged_tool_calls
+from ...telemetry.tracing import trace_tool_call
 from ...telemetry.tracing import tracer
 from ...tools.base_tool import BaseTool
 from ...tools.tool_confirmation import ToolConfirmation
@@ -590,11 +591,22 @@ async def _run_with_trace():
     )
     return function_response_event
 
-  async with _instrumentation.record_tool_execution(
-      tool, agent, invocation_context, function_args
-  ) as tel_ctx:
-    tel_ctx.function_response_event = await _run_with_trace()
-    return tel_ctx.function_response_event
+  with tracer.start_as_current_span(f'execute_tool {tool.name}'):
+    function_response_event = None
+    caught_error = None
+    try:
+      function_response_event = await _run_with_trace()
+      return function_response_event
+    except Exception as e:
+      caught_error = e
+      raise
+    finally:
+      trace_tool_call(
+          tool=tool,
+          args=function_args,
+          function_response_event=function_response_event,
+          error=caught_error,
+      )
 
 
 async def handle_function_calls_live(
@@ -818,11 +830,22 @@ async def _run_with_trace():
     )
     return function_response_event
 
-  async with _instrumentation.record_tool_execution(
-      tool, agent, invocation_context, function_args
-  ) as tel_ctx:
-    tel_ctx.function_response_event = await _run_with_trace()
-    return tel_ctx.function_response_event
+  with tracer.start_as_current_span(f'execute_tool {tool.name}'):
+    function_response_event = None
+    caught_error = None
+    try:
+      function_response_event = await _run_with_trace()
+      return function_response_event
+    except Exception as e:
+      caught_error = e
+      raise
+    finally:
+      trace_tool_call(
+          tool=tool,
+          args=function_args,
+          function_response_event=function_response_event,
+          error=caught_error,
+      )
 
 
 async def _process_function_live_helper(