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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds value by disclosing the extra behavior—reporting the weekday for the same day/month in the current year—which is not inferable from the name or schema. This goes beyond annotations, though it could mention edge cases or output format, hence not a 5.

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 sentences with zero fluff. The primary purpose is front-loaded, the format constraint is stated next, and the extra behavior follows. The source URL is a minor addition but useful for provenance. Every sentence earns its place; no redundancy with annotations or schema.

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 simple one-parameter read-only tool with an output schema (indicated by 'Has output schema: true') and annotations covering safety, the description is complete. It explains the main operation, the date format, and the auxiliary current-year lookup. No critical information for correct invocation is missing.

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 the parameter 'date' fully documented with type, format, and a matching description. The description merely repeats the YYYY-MM-DD format already present in the schema, adding no new semantic meaning. Baseline 3 is appropriate since the schema does the heavy lifting.

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 opens with a specific verb-resource pair ('Find which day of the week a given date falls on'), making the core purpose unmistakable. The date format and extra behavior (current-year weekday) add specificity, and the tool name itself differentiates it from date-related siblings like hopi_date_calculator and hopi_week_number.

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 use case is clear: when you need the weekday of a specific date. It does not explicitly exclude alternatives or name sibling tools, but the focused phrasing ('day of the week') implies this tool is for exactly that. Lacks an explicit 'when not to use' clause, but the context is unambiguous.

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