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

Annotations already declare destructiveHint=true and idempotentHint=true, so the replacement semantics are partly covered. The description adds genuine value beyond them by spelling out that it 'Replaces the previous defaults and returns them for undo' and by disclosing the undo affordance, which the structured fields do not convey.

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, zero waste, and the core action plus its effect are front-loaded before the replacement/undo clause. No padding or redundancy.

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?

With annotations covering the mutation profile and an output schema present, the description needn't explain return values, and it still flags replacement and undo. Complete enough for an agent to call it correctly, with only the missing usage routing as a gap.

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 coverage is 100%, so the schema already documents classId and every nested defaults field. The description's parenthetical mention of the field names adds only marginal meaning beyond the schema, matching the 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?

The description states a specific verb and resource ('Sets a class's assignment defaults') and enumerates the affected fields (scoring mode, timer, attempts, result release, notifications). It clearly conveys scope ('so new assignments for that class start with them'), though it does not explicitly contrast with a sibling, so 4 rather than 5.

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?

Usage is implied: the description explains the defaults apply to 'new assignments for that class,' which hints at when this tool matters. However, it names no alternative or precondition (e.g., versus update_assignment_draft or update_class), leaving routing to inference.

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