DuckDuckGo tool max_results not working as described in docs

[vinicvaz]

Checked other resources

• I added a very descriptive title to this issue.
• I searched the LangChain documentation with the integrated search.
• I used the GitHub search to find a similar question and didn't find it.
• I am sure that this is a bug in LangChain rather than my code.
• The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).

Example Code

Non-functional Code Examples:

search = DuckDuckGoSearchResults(backend="news", max_results=2)
search.invoke("Obama")  # Returns the default 4 results

wrapper = DuckDuckGoSearchAPIWrapper(region="de-de", time="d", max_results=2)
search = DuckDuckGoSearchResults(api_wrapper=wrapper, source="news", max_results=2)
search.invoke("Obama")  # Also returns the default 4 results

Error Message and Stack Trace (if applicable)

No response

Description

Hi everyone.

I've been using the DuckDuckGoSearchResults tool to perform internet searches, and I noticed that the max_results argument is not limiting the number of results as expected when used as shown in this part of the documentation: DuckDuckGoSearchResults Documentation.

However, after checking the API reference for the DuckDuckGoSearchResults class, I found that max_results is the field name and there is an alias for this field called num_results which makes it work.

This isn't a critical bug, but I think it is a mismatch between the documentation and the actual code. I'm happy to update it if necessary, but I would like to confirm if I'm correct and what exactly should be updated—whether the documentation to reflect the use of num_results or the tool's data model to accept input via the field name.

Thanks

System Info

OS: Ubuntu 24.04 LTS
Python 3.11.9

langchain==0.2.14
langchain-cohere==0.1.9
langchain-community==0.2.12
langchain-core==0.2.32
langchain-experimental==0.0.64
langchain-openai==0.1.21
langchain-text-splitters==0.2.2