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

Annotations already declare write (readOnlyHint=false), non-destructive, and idempotent. The description adds genuine behavioral context on top: it does not cancel and does not start dwell time, and it is limited to confirmed appointments. It doesn't say what happens when the appointment isn't confirmed (error vs ignored), which keeps it from 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 tight sentences, front-loaded with the core action, followed by the confirmed-only constraint and the two routing exclusions. Every sentence earns its place 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 write tool with no output schema and low schema coverage, the description covers the operation, scope constraint, and sibling routing adequately. It could still state behavior on unconfirmed appointments or the effect of estimatedDelay when status is ON_TRACK, but the essentials are present.

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%, so the description must compensate. It clarifies the status semantics (ON_TRACK vs RUNNING_LATE) and that estimatedDelay is minutes, matching the schema enum/description, but leaves appointmentId and the delay's requiredness unexplained. Partial compensation only.

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 (record) and resource (driver's check-in update on a confirmed appointment) with the exact status values. It explicitly distinguishes itself from cancel_appointment and mark_arrived, so an agent can select it without opening sibling schemas.

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 explicit when-to-use (confirmed appointments only), when-not (never cancels, doesn't start dwell time), and names the correct sibling to use instead in each excluded case (cancel_appointment, mark_arrived). Nothing is left to inference.

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