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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds meaningful behavioral context beyond that: what the calculation accounts for (holidays, weekends, make-up workdays), what the response includes (previous/next business day), and a concrete cost of $0.001 USDC on Base via x402, which is important for call planning.

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?

A single tight sentence front-loads the core operation, then appends the return detail and the cost. No wasted words, and the most decision-relevant information (what it computes) comes first.

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 two-parameter read-only tool with no output schema, the description is largely complete: it explains the computation, the output shape (boolean plus adjacent business days), and the payment mechanism. Only explicit sibling routing is missing, which is minor against the rest of the coverage.

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%, with 'date' documented as YYYY-MM-DD and 'country' as ISO alpha-2. The description adds only the phrase 'in a country,' which does not extend the format or semantics beyond what the schema already spells out, so the 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 verb-and-resource combination ('whether a date is a business day in a country') and clarifies it is holiday/weekend/make-up-day aware. It also declares the return payload (previous and next business day), which distinguishes it implicitly from siblings like business_days_add and business_days_count. It stops short of naming those siblings explicitly, so a 4 rather than a 5.

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?

The description makes clear what the tool does but offers no guidance on when to choose it versus the sibling tools. There is no 'use this instead of business_days_count' routing, no exclusions, and no stated prerequisites beyond the implicit country/date.

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