calendar_attendee_add

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

With no annotations, the description carries the burden and does well: it discloses an outward-facing side effect (Google e-mails the invitees), states the return value, and warns that confirm=true is mandatory. It does not cover edge behavior such as what happens when an address is already an attendee or whether invites can be retracted, which keeps it off a 5.

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, zero filler, with the action and the observable side effect front-loaded and the precondition trailing. Every clause earns its place.

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 4-parameter mutation with full schema coverage and no output schema, the description supplies the two things the schema cannot: the external e-mail side effect and the return value (attendee list). Remaining gaps are duplicate-invite semantics and permission requirements, which are minor.

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 the schema already documents emails, event_id, optional and confirm. The description only reinforces the confirm requirement and never mentions the optional flag, adding essentially no meaning beyond structured fields — baseline 3.

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?

Specific verb + resource ('Invite people to an event') with the mechanism and the return value stated. It is trivially distinguishable from the sibling calendar_attendee_remove, and the parenthetical about Google e-mailing guests makes the effect unambiguous.

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?

Clear context for when to call it (adding guests to an existing event) and it flags the confirm=true gating condition inline. It doesn't explicitly contrast with calendar_create (which also takes attendees) or calendar_attendee_remove, so it stops short of full alternative routing.

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