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

Annotations already cover the safety profile (readOnlyHint=true, idempotentHint=true, destructiveHint=false, openWorldHint=false), so the bar is lower. The description still adds genuine value beyond them: the required `calendar:read` scope and a prompt-injection warning that free text arrives in `untrusted_fields`. It says nothing about volume, pagination, or defaults for holds, leaving the behavioral picture incomplete.

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 with zero filler; the core operation is front-loaded and the safety/scope notes follow as compact supporting clauses. Nothing is repeated from the title or annotations unnecessarily.

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 tool with no output schema and 0% schema description coverage, the description is too thin. It helpfully names `untrusted_fields` so the agent knows how to treat returned text, but it omits date format and timezone conventions, the meaning of `include_holds`, result limits, and the difference from list_calendar_events.

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 0%, so the description carries the full burden. 'In a window' only loosely implies from/to ordering; neither date-time format, timezone, nor inclusive/exclusive boundary behavior is stated, and `include_holds` is never mentioned, so an agent cannot tell what holds are or whether they are returned by default.

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 ('List my calendar blocks') plus the scope constraint ('in a window'). It is distinguishable from get_calendar_block (singular fetch) but does not differentiate itself from the sibling list_calendar_events, so an agent must infer whether blocks and events are the same thing.

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 description supplies the auth prerequisite ('Needs `calendar:read`'), which is real guidance about preconditions, and 'in a window' implies the from/to selection use case. However, it never says when to use this versus get_calendar_block, list_calendar_events, or get_calendar_days, and gives no exclusion cases.

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