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

Annotations already declare destructiveHint=true and idempotentHint=false, and the description adds real value on top: attendees are told about the cancellation, accounts with an owner require owner approval by default, and the call costs $0.001 unless it fails. What's missing is what 'cancel' actually does to the event record (delete vs. mark cancelled) and why it is non-idempotent.

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?

Sentences are short and the primary action is front-loaded, but pricing is stated twice ('$0.001. Costs $0.001 per call; nothing if it fails.'), which wastes one of only three sentences.

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 destructive, non-idempotent, attendee-facing mutation with no output schema, the description covers approval and cost but says nothing about the result, whether attendees can be excluded, or whether the cancellation is recoverable. Adequate but with clear gaps.

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 coverage is only 50%: 'mailbox' is documented in the schema and lightly reinforced by the description, but 'event_id' has no description anywhere and the description gives no hint where to obtain it (e.g., from google_calendar_events). The prose does not compensate for the coverage gap.

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 ('Cancel an event in a mailbox's calendar') plus the attendee-notification side effect. It is clear enough to separate from google_calendar_create/events, though it never explicitly distinguishes itself from the near-identical m365_calendar_cancel or from the separate calendar_cancel booking tool.

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?

Use is implied by the verb and the 'accounts with an owner' note, which explains the approval gate the agent will hit. But there is no explicit when-to-use/when-not guidance and no routing to alternatives such as m365_calendar_cancel for Microsoft mailboxes.

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