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. The description adds genuinely useful context beyond that: the required x402 payment of $0.002 USDC on Base and the country-dependent holiday calendar. It doesn't spell out edge-case behavior (e.g., what the returned date represents), keeping it at 4.

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?

Three short sentences, front-loaded with the core function, followed by use cases, then the cost disclosure. The pricing sentence is not filler for an agent that must pay per call, so every sentence earns its place.

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 3-parameter computation with full schema coverage, the description is nearly sufficient; the phrase 'Date that is...' implies the return is a date value. It would be stronger if it stated the return format explicitly (since there is no output schema), so it lands at 4.

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 the baseline is 3. The description adds meaning beyond the schema by explaining that negative 'days' moves backward in time and that 'country' selects the business-day calendar, which the terse schema descriptions do not convey.

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 computation: a date N business days after or before a start date, parameterized by country. That is far more than a restatement of the name, but it never names the sibling tools (business_days_count, business_day) to make the add-vs-count distinction explicit.

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 concrete use contexts (T+2 settlement, SLA and filing deadlines) and clarifies the negative-days case, which tells an agent when this tool fits. It stops short of naming alternatives or stating when not to use it, so it lacks the exclusions a 5 requires.

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