Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=false, idempotentHint=false and openWorldHint=true, so the agent knows this is a non-idempotent write hitting an external system. The description adds the useful fact that the event lands on a third-party provider calendar, but says nothing about whether attendees receive invites, timezone handling, or what happens on partial failure.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

One front-loaded sentence with no filler; the scope qualification sits right where the agent needs it. It is arguably too terse for a six-parameter mutation, but nothing in it is wasted.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a non-idempotent write to an external calendar with attendees support and no output schema, the description omits key operational facts: whether invitations are sent, which calendar must already be selected/connected, and what is returned on success. An agent could call it, but not confidently.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With only 50% schema description coverage across six parameters, the description carries no parameter information at all — no mention of the required calendar/title/start/end set, the attendees structure, or the provider id convention. It does not compensate for the undocumented half of the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ("Create an event on the user's calendar") and scopes it to one external provider, explicitly distinguishing it from a Caly booking. It does not differentiate from nearby siblings like create_connection_event or create_out_of_office, but the core action is unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The parenthetical "(not a Caly booking)" implies that create_booking is the alternative for Caly-managed bookings, which is a useful routing hint. However, it never states prerequisites (a connected calendar via list_calendars/connect_calendar) or when to prefer update_calendar_event or create_connection_event.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.