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

Annotations already declare readOnlyHint=false, destructiveHint=true and idempotentHint=true, so the safety profile is partly covered. The description adds real context beyond that: the returned object, that member/trainer/services stay fixed, and that reminders follow the session. It does not explain why the call is flagged destructive (e.g. the old slot being released or overwritten), which leaves a gap worth one point.

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 sentences plus a short exclusion, with the triggering condition front-loaded and every clause carrying information about usage or preserved state. Nothing is redundant with 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?

An output schema exists, so return shape need not be spelled out, yet the description still summarises what comes back and what is preserved. It is missing only edge behaviour an agent might need, such as what happens when the new time conflicts with the member's or trainer's existing bookings.

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 all four parameters, including the expectedLastEditTime concurrency guard, are already documented in the schema; baseline 3 applies. Worse, the phrase 'its ... length stay[s] the same' sits slightly at odds with the optional durationMinutes parameter that changes the length, so the description adds no parameter clarity and a little ambiguity.

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?

Specific verb and resource: 'move a member's session to another day or time', matching the name and title. It also rules out the nearest sibling with 'Not for cancelling a session', so an agent can separate this from cancel_appointment/book_appointment without opening a 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 a clear triggering condition ('when someone asks to move a member's session') and one explicit exclusion (cancelling). It does not address the neighbouring case of booking a brand-new session instead of moving an existing one, so the routing guidance is strong but not exhaustive.

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