MCP fetch or search tools fail on a proxy or VPN
Fetch and web-search MCP servers can refuse every URL on some networks even though they are installed correctly. We hit this ourselves.
Last checked 2026-10-14 against the official docs and our own test runs.
Quick checklist
1. “Private IP” refusals
On our test machine, DNS resolved public sites to 198.18.x addresses (a proxy's fake-IP range). Fetch (reference), DuckDuckGo search and Open-WebSearch have private-address guards that then refused every URL. If fetch tools fail only on one network, this is a likely cause. Each server documents its own override; only relax it on a network you trust.
2. The website blocks bots
DuckDuckGo search sometimes got “No results” from DuckDuckGo's bot detection. That failed a search task in one of our runs even though the server was connected.
3. Try another mode of the same server
Fetch (reference)'s default (readability) mode exited with an error on our machine; its raw=true option worked.
Sources
Links checked 2026-10-14. Items marked “Our tests” come from our own harness runs, shown on each server page with the date.
App-specific guides: Claude Code · Cursor · Claude Desktop · ChatGPT (Codex) · All help