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

Beyond the annotations (which only cover readOnly/idempotent/destructive), the description discloses side effects the schema cannot: it fires a webhook, sends no carrier email, leaves appointment status unchanged, and requires scope appointments:write with Scheduler role or above. It also notes the return value. This is exactly the extra behavioral context annotations don't carry.

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?

Dense and front-loaded: the core action and its constraints come first, then exclusions, side effects, and auth in tight succession. Every sentence carries a distinct fact with 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?

With no output schema, the description supplies the return value ('updated appointment'), the auth requirement, the side effects, and the boundary conditions versus siblings. Nothing an agent needs to call this correctly is missing.

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%, so the baseline is 3, but the description adds meaning by pairing RUNNING_LATE with estimatedDelay minutes and giving a natural-language example ('30 minutes out and late'). It reinforces the enum/parameter relationship beyond the schema's field-level text.

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 ('Record the driver's own update before arrival on a CONFIRMED appointment') and names the precise state transition (sets arrivalStatus). It explicitly distinguishes itself from cancel_appointment and mark_arrived, so an agent can disambiguate without opening 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?

Gives explicit when-to-use (before arrival, on a CONFIRMED appointment) and when-not, routing to named alternatives: 'use cancel_appointment for that' and 'when the truck is physically at the dock, use mark_arrived'. The selection logic is fully spelled out.

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