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Agent Trajectory

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Agents can be difficult to holistically evaluate due to the breadth of actions and generation they can make. We recommend using multiple evaluation techniques appropriate to your use case. One way to evaluate an agent is to look at the whole trajectory of actions taken along with their responses.

Evaluators that do this can implement the AgentTrajectoryEvaluator interface. This walkthrough will show how to use the trajectory evaluator to grade an OpenAI functions agent.

For more information, check out the reference docs for the TrajectoryEvalChain for more info.

%pip install --upgrade --quiet  langchain langchain-openai
from langchain.evaluation import load_evaluator

evaluator = load_evaluator("trajectory")

API Reference:

Methods​

The Agent Trajectory Evaluators are used with the evaluate_agent_trajectory (and async aevaluate_agent_trajectory) methods, which accept:

  • input (str) – The input to the agent.
  • prediction (str) – The final predicted response.
  • agent_trajectory (List[Tuple[AgentAction, str]]) – The intermediate steps forming the agent trajectory

They return a dictionary with the following values:

  • score: Float from 0 to 1, where 1 would mean "most effective" and 0 would mean "least effective"
  • reasoning: String "chain of thought reasoning" from the LLM generated prior to creating the score

Capturing Trajectory​

The easiest way to return an agent's trajectory (without using tracing callbacks like those in LangSmith) for evaluation is to initialize the agent with return_intermediate_steps=True.

Below, create an example agent we will call to evaluate.

import subprocess
from urllib.parse import urlparse

from langchain.agents import AgentType, initialize_agent
from langchain.tools import tool
from langchain_openai import ChatOpenAI
from pydantic import HttpUrl


@tool
def ping(url: HttpUrl, return_error: bool) -> str:
    """Ping the fully specified url. Must include https:// in the url."""
    hostname = urlparse(str(url)).netloc
    completed_process = subprocess.run(
        ["ping", "-c", "1", hostname], capture_output=True, text=True
    )
    output = completed_process.stdout
    if return_error and completed_process.returncode != 0:
        return completed_process.stderr
    return output


@tool
def trace_route(url: HttpUrl, return_error: bool) -> str:
    """Trace the route to the specified url. Must include https:// in the url."""
    hostname = urlparse(str(url)).netloc
    completed_process = subprocess.run(
        ["traceroute", hostname], capture_output=True, text=True
    )
    output = completed_process.stdout
    if return_error and completed_process.returncode != 0:
        return completed_process.stderr
    return output


llm = ChatOpenAI(model="gpt-3.5-turbo-0613", temperature=0)
agent = initialize_agent(
    llm=llm,
    tools=[ping, trace_route],
    agent=AgentType.OPENAI_MULTI_FUNCTIONS,
    return_intermediate_steps=True,  # IMPORTANT!
)

result = agent("What's the latency like for https://langchain.com?")

Evaluate Trajectory​

Pass the input, trajectory, and pass to the evaluate_agent_trajectory method.

evaluation_result = evaluator.evaluate_agent_trajectory(
    prediction=result["output"],
    input=result["input"],
    agent_trajectory=result["intermediate_steps"],
)
evaluation_result
{'score': 1.0,
 'reasoning': "i. The final answer is helpful. It directly answers the user's question about the latency for the website https://langchain.com.\n\nii. The AI language model uses a logical sequence of tools to answer the question. It uses the 'ping' tool to measure the latency of the website, which is the correct tool for this task.\n\niii. The AI language model uses the tool in a helpful way. It inputs the URL into the 'ping' tool and correctly interprets the output to provide the latency in milliseconds.\n\niv. The AI language model does not use too many steps to answer the question. It only uses one step, which is appropriate for this type of question.\n\nv. The appropriate tool is used to answer the question. The 'ping' tool is the correct tool to measure website latency.\n\nGiven these considerations, the AI language model's performance is excellent. It uses the correct tool, interprets the output correctly, and provides a helpful and direct answer to the user's question."}

Configuring the Evaluation LLM​

If you don't select an LLM to use for evaluation, the load_evaluator function will use gpt-4 to power the evaluation chain. You can select any chat model for the agent trajectory evaluator as below.

%pip install --upgrade --quiet  anthropic
# ANTHROPIC_API_KEY=<YOUR ANTHROPIC API KEY>
from langchain_community.chat_models import ChatAnthropic

eval_llm = ChatAnthropic(temperature=0)
evaluator = load_evaluator("trajectory", llm=eval_llm)

API Reference:

evaluation_result = evaluator.evaluate_agent_trajectory(
    prediction=result["output"],
    input=result["input"],
    agent_trajectory=result["intermediate_steps"],
)
evaluation_result
{'score': 1.0,
 'reasoning': "Here is my detailed evaluation of the AI's response:\n\ni. The final answer is helpful, as it directly provides the latency measurement for the requested website.\n\nii. The sequence of using the ping tool to measure latency is logical for this question.\n\niii. The ping tool is used in a helpful way, with the website URL provided as input and the output latency measurement extracted.\n\niv. Only one step is used, which is appropriate for simply measuring latency. More steps are not needed.\n\nv. The ping tool is an appropriate choice to measure latency. \n\nIn summary, the AI uses an optimal single step approach with the right tool and extracts the needed output. The final answer directly answers the question in a helpful way.\n\nOverall"}

Providing List of Valid Tools​

By default, the evaluator doesn't take into account the tools the agent is permitted to call. You can provide these to the evaluator via the agent_tools argument.

from langchain.evaluation import load_evaluator

evaluator = load_evaluator("trajectory", agent_tools=[ping, trace_route])

API Reference:

evaluation_result = evaluator.evaluate_agent_trajectory(
    prediction=result["output"],
    input=result["input"],
    agent_trajectory=result["intermediate_steps"],
)
evaluation_result
{'score': 1.0,
 'reasoning': "i. The final answer is helpful. It directly answers the user's question about the latency for the specified website.\n\nii. The AI language model uses a logical sequence of tools to answer the question. In this case, only one tool was needed to answer the question, and the model chose the correct one.\n\niii. The AI language model uses the tool in a helpful way. The 'ping' tool was used to determine the latency of the website, which was the information the user was seeking.\n\niv. The AI language model does not use too many steps to answer the question. Only one step was needed and used.\n\nv. The appropriate tool was used to answer the question. The 'ping' tool is designed to measure latency, which was the information the user was seeking.\n\nGiven these considerations, the AI language model's performance in answering this question is excellent."}

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