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

Beyond the readOnly/idempotent/non-destructive annotations, it discloses the supported date window (2026-2028), the underlying data sources (CLDR weekends, pinned OpenHolidays snapshot), output provenance fields (dataset_version, source_commit, source_quality), and a direct REST fallback path with a warning not to guess other /api/* paths.

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?

Long but well-structured with labeled sections (when to use, when not to use, what it computes, example, inputs, outputs, formula, fallback, docs) and front-loaded routing guidance. Slightly bloated by enumerating output fields that are already in the output 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?

Given the tool's complexity and the existing output schema and annotations, the description still covers selection criteria, coverage limits, computation formula, provenance, and a fallback invocation path. An agent has everything needed to call it correctly and interpret the result.

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 the schema already documents all five parameters, defaults, enum, and examples. The description's 'Inputs:' list and worked JSON example restate the schema rather than adding new semantics, so the baseline 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 states a specific verb (count) and resource (working/non-working days using CLDR weekends plus nationwide OpenHolidays public events) and scopes it as a' source-labelled nationwide public-holiday reference count'. It clearly separates itself from siblings such as count_global_reference_working_days and count_global_working_days by naming the source basis.

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?

Explicit when-to-use ('when you need a source-labelled nationwide public-holiday reference count ... regional or substitute-day semantics are not required') and when-not-to-use ('regional/local or employer calendar, substitute-day rules, or dates outside 2026-2028'), plus an instruction to call it directly rather than answer from memory. Alternatives are effectively routed by the exclusion list.

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