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

Annotations already declare readOnlyHint and destructiveHint=false, so the safety profile is covered. The description adds meaningful context beyond annotations: the visibility/scope model ('calendars agents may read', user chooses in Settings), what `hidden` means, and the caldav type mapping. That is genuine behavioral disclosure layered on the annotations.

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?

Two tight sentences, front-loaded with scope, then field semantics. A touch dense with parenthetical detail but every clause conveys return-shape meaning. No filler.

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?

Output schema exists, so return-value explanation is not strictly required, yet the description clarifies `hidden`, account, type enum values, and add-event capability, which an agent needs to interpret results. Complete for a no-param lookup tool with annotations and output schema present.

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?

Zero parameters, so baseline is 4. There are no parameters to document; the description instead defines the return semantics, which is the useful information for a no-arg tool.

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+resource (list calendars) and goes further to define scope: 'the calendars agents may read', which distinguishes it from a generic calendar-list. The enumeration of returned fields tells the agent exactly what this returns.

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?

Usage is implied (an agent that needs calendar IDs before calling list_events would come here), but the description never names alternatives or states when to use this versus list_events or show_today. No explicit routing.

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