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 real substance beyond that: the South African holiday calendar, inclusive date boundaries, and the Saturday toggle. It omits what the response looks like — there is no output schema, so an agent cannot know whether it receives an integer count or a breakdown — which keeps it from a 5.

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 counting rule and then the Saturday modifier and use cases. Nothing is redundant and no sentence repeats a structured field verbatim.

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 three-parameter read-only calculation, the description covers jurisdiction, inclusivity, holiday handling, and the Saturday flag. The remaining gap is the return shape (integer count vs. list of days), which matters more than usual because no output schema exists.

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 67%, with include_saturdays documented only as a bare boolean, and the description supplies the missing meaning ('counts Saturdays as working days'). 'Inclusive' also clarifies how start and end are treated in a way the schema's 'YYYY-MM-DD' descriptions do not.

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 precise verb and resource ('Counts South African working days between two dates'), plus the defining rule set: inclusive boundaries, weekends and public holidays excluded. That scope also separates it from the sibling public_holidays tool, which would surface the holiday data this tool consumes.

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 sentence 'Useful for notice periods, payment terms and delivery dates' gives situational context that implies when to reach for it. It does not state exclusions or point at an alternative (e.g. 'use public_holidays to see which holidays were excluded'), so the guidance is implied rather than explicit.

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