Trace an agent

This page shows you how to enable Cloud Trace on your agent and view traces to analyze query response times and executed operations.

A trace is a timeline of requests as your agent responds to each query. For example, the following Gantt chart shows a sample trace from a LangchainAgent:

Sample Trace for a Query

The first row in the Gantt chart is for the trace. A trace is composed of individual spans, which represent a single unit of work, like a function call or an interaction with an LLM, with the first span representing the overall request. Each span provides details about a specific operation, such as the operation's name, start and end times, and any relevant attributes, within the request. For example, the following JSON shows a single span that represents a call to a large language model (LLM):

 {
 "name": "llm",
 "context": {
 "trace_id": "ed7b336d-e71a-46f0-a334-5f2e87cb6cfc",
 "span_id": "ad67332a-38bd-428e-9f62-538ba2fa90d4"
 },
 "span_kind": "LLM",
 "parent_id": "f89ebb7c-10f6-4bf8-8a74-57324d2556ef",
 "start_time": "2023-09-07T12:54:47.597121-06:00",
 "end_time": "2023-09-07T12:54:49.321811-06:00",
 "status_code": "OK",
 "status_message": "",
 "attributes": {
 "llm.input_messages": [
 {
 "message.role": "system",
 "message.content": "You are an expert Q&A system that is trusted around the world.\nAlways answer the query using the provided context information, and not prior knowledge.\nSome rules to follow:\n1. Never directly reference the given context in your answer.\n2. Avoid statements like 'Based on the context, ...' or 'The context information ...' or anything along those lines."
 },
 {
 "message.role": "user",
 "message.content": "Hello?"
 }
 ],
 "output.value": "assistant: Yes I am here",
 "output.mime_type": "text/plain"
 },
 "events": [],
 }

For details, see the Cloud Trace documentation on Traces and spans and Trace context.

Write traces for an agent

To write traces for an agent:

env_vars = {
 "GOOGLE_CLOUD_AGENT_ENGINE_ENABLE_TELEMETRY": "true",
 "OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT": "true",
}

fromvertexai.agent_enginesimport LangchainAgent
agent = LangchainAgent(
 model=model, # Required.
 tools=[get_exchange_rate], # Optional.
 enable_tracing=True, # [New] Optional.
)

fromvertexai.agent_enginesimport LanggraphAgent
agent = LanggraphAgent(
 model=model, # Required.
 tools=[get_exchange_rate], # Optional.
 enable_tracing=True, # [New] Optional.
)

fromvertexai.previewimport reasoning_engines
 defrunnable_with_tools_builder(model, runnable_kwargs=None, **kwargs):
 fromllama_index.core.query_pipelineimport QueryPipeline
 fromllama_index.core.toolsimport FunctionTool
 fromllama_index.core.agentimport ReActAgent
 llama_index_tools = []
 for tool in runnable_kwargs.get("tools"):
 llama_index_tools.append(FunctionTool.from_defaults(tool))
 agent = ReActAgent.from_tools(llama_index_tools, llm=model, verbose=True)
 return QueryPipeline(modules = {"agent": agent})
 agent = reasoning_engines.LlamaIndexQueryPipelineAgent(
 model="gemini-2.0-flash",
 runnable_kwargs={"tools": [get_exchange_rate]},
 runnable_builder=runnable_with_tools_builder,
 enable_tracing=True, # Optional
 )

This exports traces to Cloud Trace under the project in Set up your Google Cloud project.

View traces for an agent

For deployed agents, you can use the Google Cloud console to view traces for your agent:

1. In the Google Cloud console, go to the Vertex AI Agent Engine page.
   

   Go to Agent Engine

   Agent Engine instances that are part of the selected project appear in the list. You can use the Filter field to filter the list by your specified column.

2. Click the name of your Agent Engine instance.

3. Click the Traces tab.

4. You can select Session view or Span view.

   Click a session or span to inspect trace details, including a directed acyclic graph (DAG) of its spans, inputs and outputs, and metadata attributes.

Quotas and limits

Some attribute values might get truncated when they reach quota limits. For more information, see Cloud Trace Quota.

Pricing

Cloud Trace has a free tier. For more information, see Cloud Trace Pricing.