List grade scales

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

Annotations already declare readOnlyHint=true, so safety is covered, and an output schema documents the return shape. The description adds only that the scales are "built-in" (i.e., fixed, non-user-defined), without addressing whether they can be customized or how they relate to the conversion tools. Note a mild tension: openWorldHint=true is odd for a fixed built-in list, though the description does not explicitly contradict it.

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?

Three short sentences, front-loaded with what is returned. "Inputs: none" and the example prompt are mild padding for a zero-parameter tool, but neither is misleading and both are cheap.

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 an output schema, zero parameters, and read-only annotations, the description covers everything needed to call the tool correctly. Minor residual gap: it does not say whether these scales are the ones used by calculate_gpa/convert_grade, which would help the agent chain tools.

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?

The tool takes zero parameters, so the baseline is 4. The explicit "Inputs: none" statement usefully confirms to the agent that the empty schema is intentional rather than a truncated definition, though it adds nothing beyond the schema itself.

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 a specific verb and resource ("List the built-in grade scales") and even enumerates the returned attributes: letters, percentage ranges, grade points. It clearly reads as a catalog/listing tool, distinguishing it in practice from computing siblings like calculate_gpa or convert_grade, though it never names those alternatives.

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 example prompt ("Show me the grade scales you have built in.") gives a concrete, realistic trigger for selecting this tool, and "Inputs: none" confirms no setup is required. There are no explicit when-not conditions or named alternatives (e.g., "use convert_grade to map a specific score"), which keeps it out of the 5 band.

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