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

Annotations already cover read-only, idempotent and non-destructive, so the description only needs to add what those do not. It contributes the required `calendar:read` scope and a prompt-injection warning about `untrusted_fields`, both genuinely useful. It does not say what 'my calendar' spans (all events? all connected calendars? what time range?) or whether the result is file bytes, a URL, or text.

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 short sentences, front-loaded with the purpose and the permission requirement. The trailing untrusted_fields sentence is a bit boilerplate and its connection to an .ics export is not made explicit, but nothing is padded.

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?

There is no output schema and no parameters, so the description carries the whole burden of explaining the return value. It never says what the caller receives (inline .ics text, a download link, or an attachment), nor the default time range or calendar scope, which is a real gap for an export tool.

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 there is nothing for the description to disambiguate; baseline 4 applies. The description correctly implies the operation is unscoped/unparameterized, though it could have clarified the implicit default scope.

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 with the output format: export my calendar as an .ics file. That is distinguishable from data-reading siblings such as list_calendar_events or get_calendar_days, and from create_calendar_feed, but the description never explicitly names those siblings to draw the line.

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 .ics framing implies the usage context (getting a portable file to import elsewhere), and 'Needs `calendar:read`' flags a prerequisite. However, there is no explicit when-to-use vs. when-not guidance, and no mention of the alternative of reading events via the list/get calendar tools.

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