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

With no annotations, the description carries the full burden; it does disclose the core behavioral rule (excludes weekends and nation-specific bank holidays), which is valuable. It omits auth/premium behavior implied by 'PRO' and the access_token parameter, error behavior for unsupported regions, and whether the count is inclusive of endpoints.

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 with the resource and rule front-loaded and no filler. The leading 'PRO' token is unexplained jargon that consumes attention without conveying actionable meaning.

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 two-required-parameter calculation tool with no output schema and no annotations, the description covers the what but not the return type, date format, or subscription requirement. It is minimally viable but leaves gaps an agent must guess at before calling.

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 50% – region and access_token are documented in the schema, while 'from' and 'to' have no description at all. The prose implies 'for the nation' maps to the region parameter and that the range is date-based, but it never gives a date format, leaving a real ambiguity the schema does not resolve.

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 UK working days between two dates') plus the exclusion rule, which makes it clearly distinct from siblings like next_bank_holidays or due_date. It does not explicitly name the sibling it replaces, so a 5 is not warranted.

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 choose this over next_bank_holidays, due_date, or month_planner, and no prerequisites or exclusions are given. The only usage signal is an unexplained 'PRO' tag, which does not tell an agent whether the tool requires a subscription to call.

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