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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds real behavioral context — weekends and public holidays of 100+ countries are skipped — but then advertises 'Custom weekend days' even though no parameter in the schema supports customizing weekends, which is misleading rather than clarifying.

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 opening two sentences are near-duplicates ('Add business days to a date.' / 'Add business days.'), and the third sentence crams in a second, competing capability. A third of the text is redundant and the rest is not front-loaded around the actual add/subtract use case.

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 3-parameter, read-only calculation tool with no output schema, the description covers the key domain concept (holiday-aware business days). However, it never states the return format or how the country parameter affects the result, and its count-between-dates claim makes the tool's actual contract ambiguous.

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 date, days, and country are already documented with format examples, establishing a baseline of 3. The description's holiday-skipping note gives useful context for what 'business day' means here, but its 'custom weekend days' claim maps to no parameter and adds confusion instead of semantics.

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 first sentence names a verb and resource ('Add business days to a date'), but the second sentence repeats it verbatim and the third claims 'Count working days between two dates' — which is the job of the sibling tool business_days_between. The definition therefore blurs its own scope with a sibling rather than distinguishing itself, leaving the agent unsure whether this tool counts or adds.

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?

There is no statement of when to use this tool versus business_days_between, is_public_holiday, or public_holidays, all of which touch the same domain. The only implicit signal is that the tool adds/subtracts, but the description undercuts even that by also claiming the counting use case.

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