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MCP tool says "Please set your API key" on a no-signup server

Error: Please set your API key in the Jina AI MCP settings

What causes it

Some servers connect without a key but gate certain tools. On Jina AI, read_url worked without a key while search_web and search_arxiv returned this message as a tool error.

How to fix it

1. Get a free key at jina.ai.
2. Send it as an Authorization: Bearer header (Claude Code --header, Cursor headers, VS Code inputs). See the Jina setup guides.
3. Or use only the tools that work without a key.

Where we hit it

• Jina AI MCP test report (tested Oct 16, 2026). Setup: Claude, Claude Code, Cursor, VS Code, ChatGPT

Related fixes

• MCP tool call times out on slow servers
• MCP URL reader returns a 404 page as a normal result

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