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

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so the safety profile is covered. The description adds genuinely non-structured context: the output range (0–180 degrees, i.e. the smaller angle) and a cost of 1 credit, which is exactly the kind of quota/cost disclosure annotations cannot express.

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, each earning its place: what it computes, the return range, and the cost. The core purpose is front-loaded and nothing is padded.

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 two-parameter pure function with fully described schema and no output schema, the description covers purpose, return range, and cost — enough to call it correctly. Only minor details, such as rounding or handling of identical-hour/12-hour notation, are left unstated but are effectively immaterial.

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%, with both hour (0-23 or 1-12) and minute (0-59) documented inline. The description adds no additional meaning about parameter encoding — notably it does not clarify that the parameters are typed as strings in the schema — 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 names a specific verb and resource ('Calculates the smaller angle ... between the hour and minute hands of an analog clock') and pins down the exact quantity returned. Unlike the many vaguely named calculate_* siblings, an agent can tell precisely what this computes without opening the 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?

Usage is implied by the narrow, self-contained nature of the operation — there is no real alternative tool for clock-hand angles among the siblings. However, the description never states when to prefer it, or how to handle inputs like 12-hour vs 24-hour hours, leaving guidance to inference.

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