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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so safety is covered. The description adds real behavioral value beyond that: the pinned CLDR weekend convention, explicit holiday exclusions, provenance/dataset_version fields, and the exact formula. It does not cover rate limits, but for a pure read-only calculation this is strong.

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?

Well structured with labeled sections (what it computes, examples, inputs, outputs, formula, REST fallback, docs) and front-loaded usage guidance. It is somewhat verbose—multi-language example requests and a repeated output-field list are mildly redundant—but no single part is confusing.

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 present, return values need not be explained, yet the agent gets the formula, fallback endpoint, and docs link. For a 2-parameter, fully-annotated read-only tool, nothing needed to invoke it correctly 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%, so both parameters (date, territory) are already documented in the schema, including the accepted enum and date range. The description adds only a JSON example and restates the two inputs, matching the baseline-3 expectation when 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?

States a specific verb (check) and resource (global working day) with explicit scope: weekday/weekend only under CLDR territory convention. It clearly separates itself from siblings like check_global_public_holiday_working_day and check_uk_working_day by naming the exclusion of public-holiday rules.

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?

Gives an explicit when-to-use ('need a worldwide weekday/weekend check and have a CLDR alpha-2 territory code, but do not need public-holiday exclusions') and a detailed when-not-to-use list (holidays, substitute holidays, bank settlement, school, religious, etc.) routing to a jurisdiction-specific package. It also instructs to call directly rather than answer from memory.

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