Submission checklist

• This is a feature request, not a bug report or usage question.
• I added a clear and descriptive title that summarizes the feature request.
• I used the GitHub search to find a similar feature request and didn't find it.
• I checked the LangChain documentation and API reference to see if this feature already exists.
• This is not related to the langchain-community package.

Package (Required)

• langchain
• langchain-openai
• langchain-anthropic
• langchain-classic
• langchain-core
• langchain-model-profiles
• langchain-tests
• langchain-text-splitters
• langchain-chroma
• langchain-deepseek
• langchain-exa
• langchain-fireworks
• langchain-groq
• langchain-huggingface
• langchain-mistralai
• langchain-nomic
• langchain-ollama
• langchain-openrouter
• langchain-perplexity
• langchain-qdrant
• langchain-xai
• Other / not sure / general

Feature Description

langchain-perplexity ships a first-class PerplexitySearchResults tool (alongside ChatPerplexity and PerplexitySearchRetriever), but unlike other partner-package tools it can't be loaded by string name via load_tools:

from langchain.agents import load_tools
tools = load_tools(["perplexity_search"])  # raises: ValueError: Got unknown tool perplexity_search

This requires users to import the class directly, which is inconsistent with how other partner integrations are surfaced (e.g. serpapi, metaphor-search, google-search).

Use Case

Make PerplexitySearchResults discoverable through the canonical load_tools entry point so it's on equal footing with other search/retrieval tools. This is a small registration change with no new dependencies — langchain-perplexity is imported lazily and only when the user requests this tool by name.

Proposed Solution

Register perplexity_search in libs/langchain/langchain_classic/agents/load_tools.py with a lazy importer that raises a friendly ImportError ("Install langchain-perplexity: pip install -U langchain-perplexity") if the partner package isn't installed — same pattern used for other optional partner tools.

I have a working implementation ready (lint + 647 tests passing locally) at PR #37083, which was auto-closed because there was no linked issue. Filing this issue per the contributor policy and would like to be assigned (@james-pplx) so the PR can be reopened. Thanks!

Alternatives Considered

No response

Additional Context

Users can currently work around this by importing PerplexitySearchResults directly:

from langchain_perplexity import PerplexitySearchResults
tools = [PerplexitySearchResults()]

However, this is inconsistent with the load_tools pattern used by all other search integrations and creates an uneven developer experience for users of langchain-perplexity.