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

Goes well beyond the annotations by disclosing side-effect semantics: changing the stored e-mail redirects reminder/update e-mails to that person, and the server never fires confirmation or organizer-notification e-mails. These are exactly the non-obvious consequences an agent needs before mutating an attendee and are not present in the readOnly/destructive/idempotent hints.

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?

Three tight sentences, front-loaded with the 'WRITE:' intent marker and closing with the endpoint. Every clause carries distinct information (scope, field behavior, e-mail routing, notification non-behavior) with no redundancy.

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 mutation tool with annotations and no output schema, the description covers safety-adjacent side effects, partial-update semantics and e-mail routing well. It stops short of describing failure modes (e.g. invalid attendee_id) or the response payload, but those are minor given the annotation coverage.

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?

With 75% schema coverage the schema already documents most parameters, but the description maps the editable fields ('email, response or form answers') onto the params and adds the partial-update rule that only supplied fields change. It also names the 'attending' enum conceptually as 'response', compensating somewhat for that undocumented parameter.

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 ('changes'), a precise resource ('ONE RSVP attendee') and explicit scope ('email, response or form answers; only the fields you pass'), plus the underlying endpoint PATCH /rsvps/{id}. An agent can distinguish this update tool from the sibling list/get/create RSVP tools without reading any 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?

'only the fields you pass' implies this is a partial-update tool, which is useful context. However it never names or contrasts alternatives such as create_rsvp_attendee or get_rsvp_attendee, nor states when this tool should be preferred, so usage remains implied rather than explicit.

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