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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds real behavioral value by clarifying that it returns the series rather than generated instances and enumerating the returned fields (id, title, interval format, timezone, reminders), which helps the agent understand the shape of results.

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 sentences, front-loaded with purpose and scope before the routing instruction. The field enumeration is dense but earns its place by telling the agent what identifiers it will receive. Slightly long but no wasted framing.

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?

An output schema exists, so return values are formally documented, and the description still summarizes the key fields. For a read-only, no-argument list tool with annotations covering safety, nothing an agent needs to invoke it correctly is missing.

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?

The tool takes zero parameters, so the schema carries nothing for the description to compensate for. The baseline for a 0-param tool is 4, and nothing here misrepresents the (empty) input surface.

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 (List) and resource (the household's repeating calendar events), and immediately disambiguates scope with '(the series, not their generated instances)'. This clearly separates it from list_calendar_events and from instance-listing siblings.

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?

Explicitly routes the agent: 'Use it to find the id for update_recurring_calendar_event or delete_recurring_calendar_event.' That is clear alternative-naming guidance. It lacks an explicit when-not condition (e.g., use list_calendar_events for one-off events), so it falls just short of the top score.

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