Real-Time Information Access

Anthropic's native Web Search Tool (web_search_20260209) gives Claude the ability to search the internet during a conversation. Unlike MCP-based search integrations, this is a first-party, built-in tool that Claude can invoke autonomously when it determines real-time information is needed.

How It Works

1. Detection: Claude identifies that the question requires current information beyond its training data.
2. Search: The model generates optimized search queries and executes them against the web.
3. Dynamic Filtering: Claude can write and execute code to post-process search results, discarding irrelevant content before loading it into context.
4. Synthesis: Results are synthesized into a coherent response with automatic source citations.

API Configuration

// Enabling web search
const response = await anthropic.messages.create({
  model: "claude-sonnet-4-6",
  max_tokens: 4096,
  tools: [{
    type: "web_search_20260209",
    name: "web_search",
    max_uses: 5,               // Limit searches per request
    allowed_domains: ["docs.anthropic.com", "github.com"],
    blocked_domains: ["reddit.com"]
  }],
  messages: [{ role: "user", content: "What are the latest MCP spec changes?" }]
});

Domain Controls

For enterprise applications, you can restrict where Claude searches using allowed_domains (whitelist) and blocked_domains (blacklist). This ensures responses are grounded in trusted, approved sources only.