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

Beyond the annotations (destructiveHint=true, openWorldHint=true), it discloses concrete side effects: detail edits push to connected calendars, a cancelled status deletes the calendar event and fires appointment.cancelled, and events imported from the owner's Google Calendar are only changed locally. That is exactly the mutation-risk context an agent needs before writing.

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?

The first two sentences are well front-loaded, but the final three restate earlier content almost verbatim ('Edits are pushed to the connected calendar, and a status of cancelled removes the event. To move the time, use reschedule_appointment'). Roughly a third of the text is duplicated, wasting context.

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?

The mutation and calendar-sync behavior is covered thoroughly for a write tool with no output schema, but with 10 parameters, nested objects, and near-zero schema descriptions, the definition is silent on field-level meaning and object-merge semantics. Adequate on side effects, incomplete on inputs.

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 10% across 10 parameters, including nested customer and location objects, so the description carries the burden and largely does not. 'Send only what changes' usefully implies partial-update semantics, but it never explains whether nested objects merge or replace, nor what the status enum values or cost/duration/timezone fields mean.

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?

The opening sentence names a specific verb and resource ('Update an appointment') and the second narrows scope to detail and/or status edits. It explicitly distinguishes itself from the reschedule sibling, so an agent can route correctly without opening the 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?

It gives a clear when-to-use condition ('Edit details and/or status'), a usage rule ('Send only what changes'), and an explicit alternative for time moves: 'use reschedule_appointment'. It does not say when to prefer this tool's status=cancelled over the sibling cancel_appointment, which is the remaining routing ambiguity.

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