Web Search

The WebSearch capability gives your agent web search. Like all provider-adaptive tools, it uses the provider’s native web search when the model supports it and can fall back to a local implementation on other models.

WebSearch defaults to native-only. Backed by WebSearchTool on the native side (see Web Search Tool for provider support and configuration) — pass native=WebSearchTool(...) directly when you need full control over the native instance.

For the local side, pass local='duckduckgo' (or local=True) for a DuckDuckGo fallback (requires the duckduckgo optional group); for other search providers, use a Tavily wrapper from common_tools, the ExaSearchToolset from the Pydantic AI Harness, or any callable, Tool, or AbstractToolset.

Native configuration fields: search_context_size, user_location, blocked_domains, allowed_domains, max_uses, and OpenAI Responses’ external_web_access. The domain and max_uses constraints require native support. Setting external_web_access=False also requires native support because a local fallback cannot guarantee cached or indexed-only search.

web_search.py

from pydantic_ai.capabilities import WebSearch

# Native-only — raises on models without native web search
WebSearch()

# Native preferred; DuckDuckGo fallback (needs `pydantic-ai-slim[duckduckgo]`)
WebSearch(local='duckduckgo')

# Native preferred; custom callable as fallback
def my_search(query: str) -> str: ...
WebSearch(local=my_search)