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

Annotations cover the mutation/open-world/safety profile, but the description adds genuinely useful behavior: it sends nothing to members (silent), the change is reversible ('one more call changes the status again'), it operates without confirmation, and it requires a Cotlet API key with app access. These are exactly the traits annotations cannot express.

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?

Purpose is front-loaded, but the timing window is stated twice ('from 1 hour before it starts' and 'from 1 hour before the event starts, also after it has ended'), which is redundant padding rather than earned content.

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 no output schema, the description covers the essentials an agent needs to call it safely: timing window, silent/reversible behavior, no-confirmation policy, and auth requirement. Only the absence of explicit sibling routing keeps it short of full completeness.

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 event_id, member_ids, and the status enum are already documented, which sets the baseline at 3. The description hints at batch semantics ('many attendees in one call') but adds no syntax or value detail beyond the schema.

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 gives a concrete verb+resource: 'Set check-in status for attendees of an event', which is distinct from siblings like meetup_list_attendees or meetup_update_attendee. It is clear about what the tool does, but it never names a sibling or explicitly contrasts its role, leaving that differentiation to the agent.

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?

It communicates a real usage constraint — operable from one hour before the event until after it ends — and notes it 'runs without asking first'. However, it gives no explicit when-to-use-vs-alternatives guidance, so the selection logic against siblings such as meetup_update_attendee is only implied.

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