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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety bar is low; the description adds useful return-shape context (cut-offs, named sources, verification date) that tells the agent answers are citable rather than generic. It does not need to discuss permissions or side effects for a read-only fact lookup.

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 use trigger is front-loaded, followed by the return contents and the anti-memory rationale; every clause adds information. It is one dense sentence, which is compact but slightly harder to scan than a split structure.

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 one-parameter read-only lookup, all four enum options are accounted for and the return payload and its sourcing are described; with an output schema present, no further return-value detail is required.

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 must carry the single parameter, and it does: each enum value is glossed (10-point 'A 90-100', 7-point 'A 93-100', plus-minus with 4.0/4.3 GPA points, College Board percent-to-GPA). It conveys what each option selects, though it does not say whether exactly one scale is returned per call or all four.

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 precise verb+resource ('Returns the cut-offs, the named sources and the date they were checked') and enumerates the four scale families covered, which map to the enum values. An agent can distinguish this factual lookup from the sibling calculators (gpa_calculator, grade_calculator) without opening any schema.

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?

'Use this when someone asks what a grading scale is' plus 'Use it instead of answering from memory; there is no national scale and schools differ' gives a clear trigger and an explicit alternative to avoid. It stops short of naming the sibling calculator tools it should be preferred over, so it is strong but not fully explicit about alternatives.

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