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

With no annotations, the description carries the full behavioral burden. It discloses key traits: the Mon–Fri counting rule, holiday exclusion via Nager.Date, return breakdown (weekend and holiday), and x402 pricing ($0.01/call, USDC, eip155:8453). It does not cover rate limits or error behavior, but the core operational context is present.

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 description front-loads what the tool does, then usage, then pricing in three compact sentences. There is minor redundancy between the first and third sentences regarding weekends and holidays, and a grammatical slip ('needs to working days'), but it remains well-sized and scannable.

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 simple 3-parameter calculator with no output schema and no annotations, the description covers purpose, usage, holiday data source, and cost. It does not specify the expected date format or the exact structure of the return breakdown, but those gaps are relatively minor and not required for a correct call.

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 start, end, and country are already documented. The description adds that the country code drives holiday exclusion through Nager.Date, but it adds no date format or other syntactic detail beyond the schema. Baseline 3 applies when the schema does the heavy lifting.

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: count business days (Mon–Fri) between two dates, with weekend and holiday breakdown. It distinguishes itself from a generic date-difference calculator by specifying business days and public holiday exclusion, but it does not explicitly name the sibling tool it is not.

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?

Includes a clear when-to-use sentence: 'Use this when an agent needs to working days between dates, optionally minus public holidays.' It does not name alternative tools (e.g., calculators_date_difference_calculator or live_holidays) or state when not to use it, but the context is sufficient.

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