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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so safety is covered. The description adds meaningful context beyond the annotations: the auth requirement ('Needs the user's Cotlet API key with access to this app') and the shape of the returned fields (reservation_id and check-in status). No return format or pagination limits are described.

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?

Purpose, return contents, downstream usage, and auth needs are all front-loaded across three tight sentences with no filler. The 'Zen Planner:' prefix duplicates the title and is the only wasted token.

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 single-parameter read tool with no output schema, the description covers purpose, returned fields, auth requirement, and the downstream cross-tool chain. Nothing critical for correct invocation is missing, though an explicit note on when to prefer this over list_classes would make it fully complete.

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?

There is exactly one parameter and schema description coverage is 100% ('Class ID from list_classes'), so the schema already documents it fully. The description adds no syntax or sourcing detail beyond the schema, making the baseline 3 appropriate given how much the schema carries.

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 and resource ('get class roster') and immediately clarifies the semantics: 'Who reserved and who checked in for one class.' This distinguishes it from siblings like list_classes and check_in_member, which an agent could otherwise confuse with roster retrieval.

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?

The description tells the agent what to do with the output ('Use reservation_id with cancel_reservation and person_id with check_in_member'), which implies the workflow context. However, it never states when to call this tool versus alternatives like list_classes, nor any exclusions or prerequisites for retrieval itself.

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