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Web fetch lets the model pull a specific URL and read its contents server-side. Available on the Anthropic messages API only.

Usage

Response blocks

Fetched pages return as web_fetch_tool_result blocks:

Not available on OpenAI

Web fetch is not implemented on /v1/chat/completions or /v1/responses. For those surfaces, use web search and let the model pick a URL to cite.

Domain allow/block

Same as web search — projects can restrict reachable domains via Policy Gateway. See onboarding.
Last modified on May 3, 2026