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

Annotations already declare idempotentHint=true and destructiveHint=false; the description reinforces this in plain language ('Marking twice has the same effect') and adds the underlying POST endpoints, which is useful context an agent cannot get from annotations. It omits failure behavior (e.g., arriving a cancelled appointment), so not 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?

Three short sentences, front-loaded with the WRITE marker and the core action, followed by the edge case and then idempotency in descending priority. No filler.

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 write with no output schema, the definition covers scope, group handling, idempotency, and the underlying endpoint. Missing only error/precondition behavior (already arrived, cancelled appointment, invalid patient for a non-group appointment).

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 the schema already documents patient_id as 'Group appointments only: the patient who arrived.' The description's group-appointment sentence largely restates that, adding only the implication that omitting patient_id targets the whole single appointment.

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 and resource ('marks the patient of ONE appointment as arrived (check-in)') and flags the operation class with a leading 'WRITE:' tag. The capitalized 'ONE' plus the group-appointment note make the scope unambiguous versus sibling mutation tools like splose_update_appointment or splose_cancel_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?

Gives a concrete conditional: for a group appointment, pass patient_id to mark just that patient. It does not explicitly route the agent away from splose_update_appointment when the goal is a status change, and no preconditions (e.g., appointment must not be cancelled) are stated, so it stops short of full when/when-not guidance.

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