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

Annotations already declare readOnlyHint=true, so there is no contradiction; the description adds useful scoping behavior (student/whole-school filtering, default date). It does not go deeper into authorization or other operational constraints, but the read-only context lowers the bar, so this is adequate rather than exceptional.

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, with the core function and default behavior stated first and filter instructions second. Every word adds information, and no irrelevant details are included.

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 read-only, zero-required-parameter lookup with an output schema, the description covers what is returned and how to scope it. The only notable gap is the unexplained 'school subdomain' reference, but the rest is sufficient for an agent to call the tool successfully.

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?

Because schema property descriptions are absent (0% coverage), the description must explain parameters, and it does explain date, student, and all_classes. However, it mentions passing a 'school subdomain' even though the schema exposes no such parameter, which is ambiguous and could lead an agent to invent an unsupported argument.

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 names the exact resource (the school's substitution plan) and enumerates its contents (cancelled, moved, or substitute-taught lessons and absent teachers), which is specific enough to distinguish it from siblings like get_timetable or get_absences.

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 clearly explains scope options: pass a student for only their class or set all_classes for the whole school, and notes that the date defaults to today. It does not explicitly contrast with sibling tools, but the resource is distinct enough that an agent can infer when to use it.

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