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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds that the effect is on the trainer's schedule rather than a global calendar, but does not say whether blocking is absolute, whether existing scheduled classes are cancelled or flagged, and what happens on overlapping dates or recurring dates across years.

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?

One short sentence with the effect and scope front-loaded and no filler. It is efficient, though arguably too terse given the tool mutates scheduling state.

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 three-parameter create tool whose annotations already state the mutation and openness profile, and with fully documented parameters, the description covers what the tool does to the schedule. What is missing — conflict handling with existing classes and how a different managing trainer's view is affected — is useful but not required to call it correctly.

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%: date format YYYY-MM-DD, name example, and 'Every year' for is_recurring are all documented in the schema. The description adds no parameter-level meaning beyond that, so the baseline of 3 applies.

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 gives a concrete verb and effect ('blocks a date') plus the resource ('the trainer's schedule') and parenthetical examples tying it to vacation/holiday. It is clearly distinguishable from most siblings, but it never distinguishes itself from the closely related update_holiday or list_holidays, nor from create_schedule_slot, which also writes to the schedule.

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?

There is no guidance on when to use this versus alternatives such as update_holiday (modify an existing block) or create_schedule_slot. No prerequisites, no exclusions, no mention of what happens if a class is already scheduled on the date being blocked.

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