The MCP Server Card is written only when MCP is on

Every build used to write /.well-known/mcp/server-card.json advertising a {baseUrl}/mcp endpoint — even on a purely static deploy where nothing would ever answer there. The card, its _headers content-type and CORS rule, and its homepage Link: entry now ride the same gate as the other MCP surfaces: mcp: true in aardvark.config.yaml together with a baseUrl.

If you relied on the card, set those two after upgrading — a site that never opted in was advertising an endpoint it did not serve, and now correctly says nothing. A server card you ship by hand at static/.well-known/mcp/server-card.json still wins, gate or no gate, and still gets its _headers rule.

See Agent discovery.