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

Annotations already declare the safety profile (non-read-only, non-destructive, non-idempotent), so the description adds real value beyond them: it discloses the Teams-meeting side effect, the timezone resolution rule and the per-call cost with a no-charge-on-failure guarantee. It doesn't say whether invitees are emailed automatically, but the disclosed traits go well past what the annotations cover.

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?

The behavior is front-loaded and the sentence count is low, but the cost information is stated twice in a row ('$0.001. Costs $0.001 per call; nothing if it fails'), which wastes space in an already short description.

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 9-parameter mutation with no output schema and sparse schema descriptions, the definition covers the core action, timezone handling, Teams creation and billing. It omits how invitees are specified, what the response returns (event id?), duplicate/conflict behavior, and any permission requirements, leaving real gaps for a write 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?

Schema description coverage is only 11% (only 'mailbox' is documented), so the description must compensate. It adds meaningful meaning for start/end/timezone ('Times with an offset, or local to timezone') but leaves attendees format, subject, body, location and online_meeting unexplained in both schema and prose.

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: 'Put an event in a mailbox's calendar and invite its attendees,' produced with extras: Teams meeting and timezone-aware times. This distinguishes it from m365_calendar_cancel (cancel) and m365_calendar_events (list), but it never explicitly separates itself from the near-equivalent siblings google_calendar_create or calendar_book.

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?

No sentence says when to use this tool versus alternatives or what prerequisites exist. The agent must infer from the name that this is the write path, and there is no hint about choosing between this, google_calendar_create, or calendar_book, even though those siblings compete for the same intent.

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