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

With destructiveHint and idempotentHint already declared, the description usefully adds that the call only applies to future confirmed appointments (scope bound) and that it may send the existing cancellation communication (external side effect). It does not say whether cancellation is reversible or what happens to downstream state, but the annotation covers the safety profile.

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?

Two compact sentences with the action first and prerequisites after. The middle sentence is slightly list-like and could read more smoothly, but no sentence is wasted.

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?

An output schema exists, so return values need not be explained. For a destructive open-world mutation, the description covers scope, prerequisites, and the communication side effect; the only real shortfall is not unpacking the required idempotencyKey/note parameters.

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 0%, so the description carries the full burden, yet it only glosses expectedVersion ('current request version') and confirmed ('explicit confirmation'). It refers to 'appointmentId or proposalId' rather than the actual target/targetId fields, and never mentions sessionToken, idempotencyKey, or note, leaving a meaningful mapping gap for a 7-parameter tool.

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 ('Cancel a future confirmed appointment or withdraw the customer's own pending proposal'), covering both modes the enum encodes. It does not explicitly name or contrast with nearby siblings such as viewings.decline_proposals or viewings.respond_to_proposal, so an agent must infer the routing.

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 concrete prerequisites: identifiers come from viewings.get_details, the current request version is required, and explicit confirmation is needed. It stops short of stating when not to use this versus decline_proposals or respond_to_proposal, so the exclusion case is left implicit.

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