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

Annotations already declare destructiveHint=true and idempotentHint=true, but the description adds real behavioral context the annotations cannot: omitted optional fields are not sent (partial-send semantics), times are converted to UTC, and the customer may be notified as a side effect. It does not state permission requirements or what the response contains, keeping it just short of the top mark.

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?

Four short sentences, front-loaded with the WRITE marker and the core action, then prerequisite, then side effects, then transport detail. Every sentence carries distinct information with no restatement of the title.

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 12-parameter destructive mutation with a nested custom_fields object and no output schema, the description covers action, prerequisites, side effects and timezone handling. Minor gaps remain around authorization requirements and whether notification is unconditional, but nothing essential for correct invocation 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 description coverage is 100%, so the schema baseline is 3; the description earns above that by explaining the semantics of omission for optional fields and calling out that all of staff, service, start, end and customer_name are mandatory regardless. It adds no format detail beyond the schema (ISO 8601, custom_fields naming) because the schema already carries it.

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?

Opens with an explicit mode marker ('WRITE:') plus a specific verb pair and resource ('reschedule or edit an existing appointment'), which cleanly separates it from bookafy_create_appointment and bookafy_cancel_appointment. It even names the underlying endpoint (PUT /api/v3/appointments/{id}), leaving no ambiguity about what is being changed.

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 precondition workflow ('read current values with bookafy_list_appointments first') and enumerates the values that must be supplied. It does not explicitly exclude adjacent cases — e.g. that removing an appointment should go to bookafy_cancel_appointment — so it is a strong but not fully disambiguating guideline.

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