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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered, and the description adds two non-trivial constraints: the max 3-year span and a $0.002 USDC cost via x402 on Base. Disclosing a paid, metered call is exactly the kind of thing the agent needs before invoking.

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?

Two sentences, front-loaded with the core semantics, then the hard limit and the payment notice. No filler and nothing buried.

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 still conveys what comes back — a count plus the weekday holidays — along with the 3-year cap and the cost. Return formatting details are the only meaningful gap, and they are minor for a scalar-count tool.

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 country (ISO alpha-2), start and end (YYYY-MM-DD) are already documented. The description only adds the inclusivity of the [start, end] boundary, which is a modest but real clarification beyond 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?

The description states a specific verb-and-resource pairing: counting business days within an inclusive [start, end] range, plus the weekday holidays in that range. That is clearly distinct from business_day (single day), business_days_add (arithmetic on a date) and holidays (holiday lookup), even though those siblings are never named.

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?

Usage is implied rather than stated: range counting with an inclusive boundary is described, but there is no explicit 'use this when you need a count rather than a list' or pointer to business_days_add for offsetting. An agent can infer the choice, but the description does not make it.

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