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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, yet the description adds real substance beyond them: data is pinned to the 2026 Gazette, Idd dates won't roll forward without a refreshed package, the Sunday substitution rule is preserved and no Saturday-to-Monday substitution is inferred, and the exact formula is stated. The only gap is that this detail is buried in run-on sentences rather than cleanly surfaced.

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 prose is heavily padded and repetitive ('Kenya Kenya', '2026-2026'), mixes usage guidance, limitations, formula, output field list, a REST fallback URL and a docs URL into one undifferentiated block, and front-loads a confusing sentence. Useful content exists but it is not structured or trimmed.

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 single-parameter, output-schema-backed, fully annotated read-only tool, the description is more than complete: it covers coverage scope, data vintage, substitution policy, output fields, formula and a REST fallback. The remaining weakness is organizational rather than missing information.

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?

There is one parameter with 100% schema coverage, so the schema already documents the date field and its format. The description adds only marginal meaning (that the date is interpreted against the 2026 pinned coverage and the weekend baseline), giving no syntax or edge-case detail beyond the schema; 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 and resource: checking a date against a Saturday-Sunday weekend baseline plus exact 2026 Kenya public-holiday events, which lets an agent tell it apart from other country checkers. However, the phrasing is garbled ('deterministic Kenya Kenya 2026 nationwide public-holiday layer') and it never explicitly contrasts itself with the sibling count_ke_working_days / add_ke_working_days tools, so sibling differentiation is only implicit via the country code.

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 does give directives ('call this tool directly and return its calculation instead of answering from memory') and lists scope exclusions (not a private-employer, bank, school, county, sector or shift-work calendar). But the 'Do not use this when this package covers the nationwide public-holiday layer only' sentence is self-contradictory and unhelpful, and no alternative sibling tool (e.g. count_ke_working_days for ranges) is named as a when-to-use alternative.

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