feat: add Serper search engine support (#762)

* feat: add Serper search engine support

* docs: update configuration guide and env example for Serper

* test: add test case for Serper with missing API key

.env.example

@@ -24,10 +24,11 @@ ENABLE_MCP_SERVER_CONFIGURATION=false
 # Otherwise, you system could be compromised.
 ENABLE_PYTHON_REPL=false
 
-# Search Engine, Supported values: tavily, infoquest (recommended), duckduckgo, brave_search, arxiv, searx
+# Search Engine, Supported values: tavily, infoquest (recommended), duckduckgo, brave_search, arxiv, searx, serper
 SEARCH_API=tavily
 TAVILY_API_KEY=tvly-xxx
 INFOQUEST_API_KEY="infoquest-xxx"
+# SERPER_API_KEY=xxx # Required only if SEARCH_API is serper
 # SEARX_HOST=xxx # Required only if SEARCH_API is searx.(compatible with both Searx and SearxNG)
 # BRAVE_SEARCH_API_KEY=xxx # Required only if SEARCH_API is brave_search
 # JINA_API_KEY=jina_xxx # Optional, default is None

docs/configuration_guide.md

@@ -204,6 +204,24 @@ The context management doesn't work if the token_limit is not set.
 
 ## About Search Engine
 
+### Supported Search Engines
+DeerFlow supports the following search engines:
+- Tavily
+- InfoQuest
+- DuckDuckGo
+- Brave Search
+- Arxiv
+- Searx
+- Serper
+- Wikipedia
+
+### How to use Serper Search?
+
+To use Serper as your search engine, you need to:
+1. Get your API key from [Serper](https://serper.dev/)
+2. Set `SEARCH_API=serper` in your `.env` file
+3. Set `SERPER_API_KEY=your_api_key` in your `.env` file
+
 ### How to control search domains for Tavily?
 
 DeerFlow allows you to control which domains are included or excluded in Tavily search results through the configuration file. This helps improve search result quality and reduce hallucinations by focusing on trusted sources.

src/config/tools.py

@@ -17,6 +17,7 @@ class SearchEngine(enum.Enum):
     ARXIV = "arxiv"
     SEARX = "searx"
     WIKIPEDIA = "wikipedia"
+    SERPER = "serper"
 
 
 class CrawlerEngine(enum.Enum):

src/tools/search.py

@@ -8,6 +8,7 @@ from typing import List, Optional
 from langchain_community.tools import (
     BraveSearch,
     DuckDuckGoSearchResults,
+    GoogleSerperRun,
     SearxSearchRun,
     WikipediaQueryRun,
 )
@@ -15,6 +16,7 @@ from langchain_community.tools.arxiv import ArxivQueryRun
 from langchain_community.utilities import (
     ArxivAPIWrapper,
     BraveSearchWrapper,
+    GoogleSerperAPIWrapper,
     SearxSearchWrapper,
     WikipediaAPIWrapper,
 )
@@ -33,6 +35,7 @@ LoggedTavilySearch = create_logged_tool(TavilySearchWithImages)
 LoggedInfoQuestSearch = create_logged_tool(InfoQuestSearchResults)
 LoggedDuckDuckGoSearch = create_logged_tool(DuckDuckGoSearchResults)
 LoggedBraveSearch = create_logged_tool(BraveSearch)
+LoggedSerperSearch = create_logged_tool(GoogleSerperRun)
 LoggedArxivSearch = create_logged_tool(ArxivQueryRun)
 LoggedSearxSearch = create_logged_tool(SearxSearchRun)
 LoggedWikipediaSearch = create_logged_tool(WikipediaQueryRun)
@@ -102,6 +105,14 @@ def get_web_search_tool(max_search_results: int):
                 search_kwargs={"count": max_search_results},
             ),
         )
+    elif SELECTED_SEARCH_ENGINE == SearchEngine.SERPER.value:
+        return LoggedSerperSearch(
+            name="web_search",
+            api_wrapper=GoogleSerperAPIWrapper(
+                k=max_search_results,
+                serper_api_key=os.getenv("SERPER_API_KEY", ""),
+            ),
+        )
     elif SELECTED_SEARCH_ENGINE == SearchEngine.ARXIV.value:
         return LoggedArxivSearch(
             name="web_search",

tests/unit/tools/test_search.py

@@ -5,6 +5,7 @@ import os
 from unittest.mock import patch
 
 import pytest
+from pydantic import ValidationError
 
 from src.config import SearchEngine
 from src.tools.search import get_web_search_tool
@@ -56,6 +57,20 @@ class TestGetWebSearchTool:
         tool = get_web_search_tool(max_search_results=1)
         assert tool.search_wrapper.api_key.get_secret_value() == ""
 
+    @patch("src.tools.search.SELECTED_SEARCH_ENGINE", SearchEngine.SERPER.value)
+    @patch.dict(os.environ, {"SERPER_API_KEY": "test_serper_key"})
+    def test_get_web_search_tool_serper(self):
+        tool = get_web_search_tool(max_search_results=6)
+        assert tool.name == "web_search"
+        assert tool.api_wrapper.k == 6
+        assert tool.api_wrapper.serper_api_key == "test_serper_key"
+
+    @patch("src.tools.search.SELECTED_SEARCH_ENGINE", SearchEngine.SERPER.value)
+    @patch.dict(os.environ, {}, clear=True)
+    def test_get_web_search_tool_serper_no_api_key(self):
+        with pytest.raises(ValidationError):
+            get_web_search_tool(max_search_results=1)
+
     @patch("src.tools.search.SELECTED_SEARCH_ENGINE", SearchEngine.TAVILY.value)
     @patch("src.tools.search.load_yaml_config")
     def test_get_web_search_tool_tavily_with_custom_config(self, mock_config):