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

Annotations already declare readOnlyHint=true, so the safety profile is covered by structured data. The description adds only the fact that this is a single-item lookup keyed by three identifiers; it says nothing about error behavior for a missing event, permissions, or rate limits, so it is minimum viable given 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?

A single front-loaded sentence that names the action, the resource, and the lookup keys with zero filler. Nothing could be removed without losing information.

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 simple read-only getter with three fully documented required parameters and no nested objects, the description plus schema covers what an agent needs to invoke it. The absence of an output schema means the return shape of a 'calendar event' is unspecified, but that is a minor gap for a straightforward lookup.

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%: each parameter is documented in the schema, including the hint that accountId and providerCalendarId come from list_accounts and list_calendars. The description restates the three keys but adds no format or constraint detail beyond the schema, so baseline 3 applies.

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 ('Get a single calendar event') and names the three lookup keys, which cleanly separates it from list_events and get_sync. It does not explicitly name the sibling alternative, but the singular/plural distinction makes the purpose 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 requirement that the caller already possess account, calendar, and event IDs implicitly signals this is a direct lookup rather than a search, but there is no explicit statement of when to use this over list_events or what to do if the IDs are unknown. Usage is implied rather than stated.

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