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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds real value: weekends and public holidays are skipped, observed Monday holidays included, and answers carry as_of plus the official source. It does not say what happens for dates outside the 2026–2027 window or on invalid input, which keeps it from 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?

Front-loads the resource, then packs the mode logic into one dense but readable passage, ending with a concrete example input. Slightly run-on, but every clause carries information.

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 read-only, no-output-schema lookup tool, the description covers data source, coverage years, weekend/holiday skipping, all four calling modes, and the shape of the answer (as_of, source). 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 coverage is 100%, so individual parameters are already documented; the description goes further by explaining how parameters compose (date alone vs. with add vs. with to) and that the start date is not counted. That compositional meaning genuinely exceeds the schema.

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 the specific resource (Singapore public holidays and working days, MOM data) and enumerates the four query modes, so an agent can tell exactly what it computes. No sibling covers this domain, and the scope is unambiguous.

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?

Explicitly maps each argument combination to an outcome: date alone for a yes/no check, from+add for offsetting, from+to for counting between dates, year for listing holidays. This is a complete when-to-use guide with no inference required.

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