Add a guest to an appointment

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

Annotations already signal mutation via readOnlyHint=false and destructiveHint=true, and the description adds meaningful behavioral detail: it modifies the appointment by adding a guest, triggers invitation/update delivery, and limits calls to one guest. It does not contradict the annotations.

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 with no wasted words. The core action is front-loaded and the constraints are packed efficiently into the second sentence.

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 simple three-parameter mutation with an output schema and annotations, the description covers the essential information: action, prerequisite, and per-call limit. It could mention duplicate handling or permanence, but those are not critical to making a correct first call.

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 33%, but the description compensates by explaining the attendeeId's origin ('returned with appointment details') and the email's purpose ('receive the invitation and updates'). appointmentId is not detailed, but its role is obvious from the tool name and context.

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?

The description opens with a specific verb and resource: 'Add one guest email to an appointment'. It also clarifies the downstream effect ('so they receive the invitation and updates'), making the tool's purpose unambiguous and distinct from sibling tools like create_contact or book_appointment.

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 gives a clear prerequisite: 'Requires the attendeeId returned with appointment details', and a usage constraint: 'accepts one guest per call'. It does not explicitly name alternatives or state when not to use the tool, but the context is strong enough for an agent to select it appropriately.

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