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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 or Exa wrapper from common_tools, or any callable, Tool, or AbstractToolset.

Native constraint fields: search_context_size, user_location, blocked_domains, allowed_domains, max_uses. The domain and max_uses constraints require native support (the shipped DuckDuckGo fallback doesn’t enforce them).

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)