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

Annotations already declare write, non-idempotent, non-destructive behavior; the description adds that check-in sets checked_at to now, supports undo, and fails for non-participants. It does not spell out repeated check-in semantics, but otherwise adds meaningful behavioral context beyond 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?

Four short sentences, front-loaded with WRITE and the action, with no wasted words. The endpoint is included as useful implementation context without bloating the 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 two-parameter mutation with annotations and no output schema, the description covers the input source, write effect, undo behavior, failure condition, and endpoint. It does not describe the response payload, but that is not essential for correct invocation.

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 100% and both parameters are documented in the schema. The description still adds value by explaining where attendee_id comes from and that checkin=true sets checked_at to now, beyond the schema's simple true/false toggle.

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 action (check a participant in at the event) and its inverse (undo the check-in), plus the PATCH endpoint. This clearly distinguishes it from sibling tools like remove_attendee, register_people, and create_* operations.

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?

Tells the agent to source the participant id from eventee_list_participants and notes that the call fails if the person is not a participant of the event. Clear usage context, though it does not explicitly name alternative tools for adjacent workflows.

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