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

Annotations already declare readOnly, idempotent, closed-world and non-destructive, so safety is covered. The description adds genuinely extra behavioral context: the pinned 2026-2027 range, the MOM/CLDR data basis, dataset_version/source_quality provenance, the per-date accumulation formula, and a REST fallback endpoint to use on failure. It stops short of noting failure modes or rate/limit behavior.

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 front-loaded with 'Use this when' first, then clearly labeled sections (when-not, what it computes, inputs, outputs, formula, fallback, docs). It is longer than needed because the inputs/outputs lists and the complete JSON example duplicate structured data already present in the schema and 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?

For a range-calculation tool with an output schema, an agent has everything needed: exact date-range limits, inclusion flags, data source, and a fallback path. The enumerated outputs are redundant with the output schema but nothing required 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 each parameter is already documented with type, format and defaults. The description only restates the input list and repeats a JSON example that duplicates the schema's own examples, adding no syntax or semantic detail the schema lacks. Baseline 3 applies 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?

The description states a precise verb+resource with scope: counts Singapore working/non-working dates in a 2026-2027 range using MOM public holidays and the CLDR Sat/Sun baseline. It is far more specific than the title. However, it never names the obvious siblings (add_singapore_working_days, check_singapore_working_day) to route the agent between the count/add/check variants, so sibling differentiation is only implicit.

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 an explicit when-to-use ('when you need an auditable Singapore working-day count for a pinned year'), an explicit when-not-to-use ('Do not use this when you need an employer-specific rest-day roster, bank/exchange closures or future years'), and a directive to call the tool rather than compute from memory. The conditions that select this tool are stated outright.

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