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

Annotations already establish read-only, idempotent, non-destructive, and closed-world behavior. The description adds useful context beyond annotations: the exact computation formula, deterministic output, 2026 authority-event scope, full output field list, and a specific REST fallback endpoint with a warning not to guess other paths. It does not mention authentication or rate-limit behavior, so it is strong but not exhaustive.

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 description is well-sectioned and front-loads usage guidance, but it is long for a one-parameter date-check tool. It repeats schema-provided input examples, lists output fields even though an output schema exists, and contains minor typos ('Brazil Brazil', '2026-2026'). Several sentences earn their place, but redundancy and length reduce conciseness.

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?

Given the simple schema, rich annotations, and an available output schema, the description provides everything an agent needs: scope boundaries, exact computation formula, example input, fallback endpoint, and documentation link. No critical context is missing for correct invocation.

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%, and the schema already documents the single date parameter with format and examples. The description adds only a restatement of the input name and a JSON example, which is redundant with the schema. Baseline 3 is appropriate when the schema carries the parameter documentation.

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 ('Checks') and resource ('date') against a Brazil federal executive (SIPEC) calendar, and explicitly distinguishes its scope from private, state, municipal, sector, and employer calendars. It does not explicitly distinguish itself from sibling add_br_working_days or count_br_working_days, so it falls short of a perfect sibling differentiation score.

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?

It gives explicit when-to-use guidance ('Use this when you need a deterministic Brazil... result') and when-not-to-use guidance by excluding non-federal calendars. However, it does not name an alternative sibling tool to use for those excluded cases, which the rubric requires for a 5.

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