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

It explains the otherwise confusing readOnlyHint=false by stating the tool 'reads or computes only' but is charged per call, and adds pricing/billing behavior (first 25 free, failed calls free, $0.003 via x402 USDC or card key). It does not account for openWorldHint=true or idempotentHint=false, so the read-only explanation is the main but not the only behavioral gap.

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-loaded with the resource and coverage, then usage, then commercial and safety notes in a logical order with no wasted sentences. It is a single dense paragraph, and the pricing detail is somewhat bulky for a tool description, but every clause carries information an agent needs.

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 no output schema, the description does the work of describing returns (date, local/English name, observed weekday) and the valid year window and country set. Pricing, safety posture and coverage are all present; only the openWorld/idempotency hints go unexplained.

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% and both parameters are already documented there, including the country code list and the year range/default. The description adds only a redundant example, correcting nothing beyond confirming the effective 2024-2100 window, so 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?

States a specific resource (nationwide public holidays) with explicit coverage (US federal, UK England and Wales, SE, DE, FR, NO, DK, FI) and enumerates the returned fields (date, local and English name, observed weekday). This clearly separates it from siblings like country, time, sun and moon.

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 concrete use contexts (scheduling, delivery dates, business-day maths) plus a worked example (country=SE, year=2026), which is enough to place the tool. It stops short of stating when NOT to use it or naming a sibling alternative (e.g., time or country) for non-holiday date needs.

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