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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false, so the safety profile is covered. The description adds genuine behavioral value by disclosing what the listing surfaces (primary flag, editability, time zones), which helps an agent decide what to read off the result.

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, purpose first, usage second, followed by a compact 'Example: {}' that correctly signals the call needs no arguments. Nothing is redundant.

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 an output schema present, annotations covering safety, and full parameter documentation, the description only needs to supply purpose, routing, and return-shape hints — all of which it does. An agent has everything required to invoke and interpret it.

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 both account_id and profile_id are already documented at baseline. The phrase 'one account or all' echoes account_id semantics but the description says nothing about profile_id filtering, so it adds little beyond the schema.

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 ('Lists calendars') plus scope ('for one account or all') and what the output distinguishes ('primary', 'which you can edit', 'time zones'). That is enough to separate it from calendar_list_events and calendar_create_event without opening a schema.

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 names the downstream use: 'Use it to choose a `calendar_id` for calendar_create_event.' That gives a clear trigger to call it. It stops short of stating when not to call it or naming an alternative discovery path, so it is strong but not exhaustive.

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