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

Annotations already signal a mutating, destructive operation, and the description confirms the state change. It adds the useful `[requires scope: book]` auth context, but it does not disclose reversibility, idempotency, or broader effects of the check-in.

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 description is a single, front-loaded sentence with no filler. It states the action first and appends the scope requirement compactly.

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 simple two-parameter mutation, it covers the action, parameter mapping, and required scope. However, with destructiveHint=true and no output schema, it would benefit from noting whether check-in is reversible and what happens on repeated calls.

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 burden. It implicitly maps client_id to 'client' and class_session_id to 'class session,' which is helpful, but it does not explain the nature or format of the IDs beyond that.

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 description uses a specific verb ('Mark') and resource ('a client ... for a class session'), with '(arrived)' clarifying the exact meaning of check-in. This clearly distinguishes it from sibling tools like add_client_to_class or remove_client_from_class.

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 clear context for when to use the tool: when a client has arrived for a class session. It does not explicitly name alternatives or state exclusions, but the arrival context is enough to guide selection.

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