How do I fix the 'python_repl_ast is not a valid tool' error when using a CSV agent?

Below is one common explanation and solution:

It looks like your agent is trying to call the tool under the name "python_repl_ast" but the tool provided isn’t registered under that name. In our LangChain examples the interactive Python execution tool is generally set up as "python_repl" (or another properly registered name) before it’s passed to an agent. In other words, if you want to use a tool called "python_repl_ast" you must first create and register it with that exact name.

For example, you might do something like this:

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from langchain.tools import Tool

python_repl_ast = Tool(
    name="python_repl_ast",
    description=(
        "A Python shell that uses the AST to execute Python commands. "
        "Ensure that your command is valid Python and that you print outputs "
        "if you want to see them."
    ),
    func=python_repl.run,  # assuming you have a function python_repl.run that executes the code
)

Then, when you create your CSV (or SQL) agent, make sure you include this tool in the tool list. For example:

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from langchain_community.agent_toolkits import create_sql_agent

agent_executor = create_sql_agent(llm, db=db, tools=[python_repl_ast], agent_type="openai-tools", verbose=True)

If you mistakenly gave your tool the wrong name or if your agent is configured to expect a tool named "python_repl" instead of "python_repl_ast", then update your configuration so that the names match. (Versions of agents may expect different tool names.)

In summary, verify that:

1. You have instantiated the tool with the exact name you want (“python_repl_ast”).
2. Your agent is being provided with that tool (or the tool matching the name it expects).

Double‐check your tool registration code and the list of tools you pass to your agent, and adjust the names accordingly. This should resolve the "not a valid tool" error.