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

Annotations only declare destructiveHint=true; the description goes beyond that by disclosing the return value ('Returns the attendance id') and the exact reversal tool, which matters for a mutating call. It still omits auth/permission requirements and what happens on duplicate registration or full capacity, so it is not fully transparent.

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?

Three short sentences, front-loaded with the action and its variants, then the return value, then the undo route. No filler, and the API endpoint hint is compactly appended.

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?

No output schema exists, but the description compensates by stating the returned attendance id, and all four parameters are covered by the schema. Missing only secondary behavioral detail (idempotency, capacity/failure behavior, auth), which is acceptable for a single-purpose booking call.

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 every parameter is already documented (customer, event_id, customer_membership, comped). The description only restates the membership-or-comped choice at a high level and adds no format or edge-case detail, so the schema does the heavy lifting — baseline 3.

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+resource ('Register a customer for a class or appointment'), clarifies the optional mechanisms (specific membership or comped), and names the inverse sibling goteamup_unregister_customer_from_event, which no other tool covers. An agent can distinguish it from list/get/confirm tools 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?

Explicitly routes the agent to goteamup_unregister_customer_from_event as the undo path, and distinguishes the two booking modes (membership-backed vs comped/free). It does not state prerequisites such as the event needing capacity or the customer needing to exist, but the when-to-use context is otherwise clear.

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