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

With no annotations, the description must carry behavioral disclosure: it usefully states that calendar-day results are rolled to the next working day and mentions a statutory 30-day default. It says nothing about how `from` defaults when omitted, whether paid subscription (access_token) is mandatory, or what the result looks like.

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?

Two compact sentences, front-loaded with the operation and immediately followed by the rolling/default nuance. The 'PRO.' marker is noise but costs almost nothing.

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 5-parameter tool with no annotations and no output schema, the description covers the core calculation rule but leaves the auth requirement, `from` default, and return shape unaddressed, forcing the agent to infer from the schema fragment.

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 only 40% (`days`, `from`, `working` have no schema descriptions). The description partially compensates by contrasting working days vs calendar days (mapping to `working`) and naming a 30-day default, but never explains `from`'s format/default or whether negative `days` are allowed.

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?

Clear verb+resource: add N working or calendar days to a date to produce an invoice/contract due date. It is distinguishable from siblings like working_days (which presumably counts) and tax_deadlines, though the description never names an alternative explicitly.

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 'Invoice/contract due date' framing implies the use case, and 'Includes Late Payment Act 30-day default' hints at a legal-basis scenario, but there is no explicit when-to-use / when-not guidance or routing to working_days for pure day counting.

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