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

With no annotations, the description carries the full burden. It usefully discloses the commercial model ('Auth mode: paid', '$0.005 per call'), which is real behavioral context. But it never states the return type, and critically never resolves which calendar the year/month/day inputs use (Gregorian vs Jalali) or what 'weekend' means for the Iranian locale.

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 functional content is a single sentence that is duplicated verbatim as both 'Summary' and 'Source description'. It is wrapped in origin URLs, hostnames, brand strings, family keys, endpoint paths, keyword lists, and pricing, so the actual signal is buried and not front-loaded.

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 2-parameter tool with 0% schema coverage, nested objects, no annotations, and no output schema, the description should pin down the calendar system, the definition of a weekend, and the result shape. None of these are addressed, so an agent cannot call it with confidence.

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 0% and both parameters are nested {year, month, day} objects with no ranges, no descriptions, and no calendar indicator. The description adds nothing beyond implying 'from' and 'to' are dates, so it fails to compensate for the coverage gap on a genuinely ambiguous input shape.

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 core sentence 'Count business days between two dates (weekends excluded)' gives a specific verb and resource with a scope qualifier. It does not, however, differentiate from adjacent siblings such as iran_holiday_check or iran_holidays, leaving the agent to infer whether holiday-aware counting exists elsewhere.

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 three 'Use case' lines sketch plausible contexts (delivery estimates, task duration), which is more than nothing. But there are no exclusions or named alternatives, and one use case ('add working days to a deadline') describes an operation the from/to signature cannot perform, which is mildly misleading.

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