Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish readOnlyHint=true and openWorldHint=false, and the description adds genuinely useful behavior beyond that: it searches 3,000+ capabilities (n8n nodes, OpenAPI, MCP) and, distinctively, reports a gap rather than silently substituting a different app. That no-substitution policy is exactly the kind of behavioral trait an agent needs. It stops short of describing plan shape or failure modes.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.