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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower, and the description adds real value beyond them: the return format (.ics), the exact event contents and alert timing, and 'Nothing is stored' (no persistence). It doesn't cover rate limits or formatting quirks, but adds substantive behavioral context.

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?

Front-loaded with the purpose and then details the return artifact without padding. The final sentence about get_cancel_steps is slightly tangential to this tool's own invocation but earns its place as routing context.

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?

With no output schema, the description carries the burden of explaining the return value and does so thoroughly (event contents, alerts, no storage). An agent has enough to invoke correctly; only explicit exclusions for when not to call it are 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?

Schema description coverage is 100%, so the schema already documents country, service, and renews_on; baseline is 3. The description references renews_on's role indirectly but adds no format or semantic detail beyond what the schema supplies.

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 (get/returns) and resource (calendar reminder for the last safe day to cancel) and describes the concrete artifact returned: an .ics all-day event with steps, official link, and 9am alerts. It is distinguishable from the sibling get_cancel_steps, which yields a link, not a calendar file.

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?

It gives usable context by noting get_cancel_steps surfaces this link as add_to_calendar whenever renews_on is provided and the day hasn't passed, effectively describing the condition under which this tool applies. It stops short of an explicit when-not-to-use statement, so no code-5 routing guidance.

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