ValueError: Prompt missing required variables: {'agent_scratchpad'}

[Ma-Zijing]

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Example Code

retriever_tool = create_retriever_tool(retriever, "similar_app_search",
                                           "Search for information about the given Android app. For any questions about the given Android app, you must use this tool!", )
tools = [retriever_tool]
role_prompt = (
        "Given app name to you, you need to search related information."
    )
prompt = ChatPromptTemplate.from_messages(
  [
     ("system", role_prompt),
     ("human", "What is {app_name}?"),
  ]
)

llm = get_llm("llama3")
agent = create_tool_calling_agent(llm, tools, prompt)

Description

Hi! I try to build an agent to retrieve related information from the vectorstore. However, the create_tool_calling_agent method raises an error ValueError: Prompt missing required variables: {'agent_scratchpad'}. I have no idea why the error occurs and where is the 'agent_scratchpad'.

System Info

langchain 0.1.17

[dosubot[bot]]

To resolve the ValueError: Prompt missing required variables: {'agent_scratchpad'} error, you need to ensure that your ChatPromptTemplate includes the agent_scratchpad key as a MessagesPlaceholder. Here is how you can modify your code:

from langchain.agents import AgentExecutor, create_tool_calling_agent, tool
from langchain_core.prompts import ChatPromptTemplate

retriever_tool = create_retriever_tool(
    retriever, 
    "similar_app_search",
    "Search for information about the given Android app. For any questions about the given Android app, you must use this tool!"
)
tools = [retriever_tool]
role_prompt = "Given app name to you, you need to search related information."

prompt = ChatPromptTemplate.from_messages(
    [
        ("system", role_prompt),
        ("human", "What is {app_name}?"),
        ("placeholder", "{agent_scratchpad}"),
    ]
)

llm = get_llm("llama3")
agent = create_tool_calling_agent(llm, tools, prompt)
agent_executor = AgentExecutor(agent=agent, tools=tools, verbose=True)

# Example usage
agent_executor.invoke({"input": "What is the value of similar_app_search for 'example app'?"})

Ensure that the prompt includes the agent_scratchpad placeholder as shown above. This placeholder is necessary for the create_tool_calling_agent function to work correctly ^[1][2].

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