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

Annotations already cover read-only/idempotent/no-open-world, and the description goes well beyond them: it discloses the return contents (result date, day count, skipped dates with reasons), the 1,000-entry truncation cap with skipped_truncated flag and exact skipped_total, and the $0.05 x402/USDC-on-Base pricing requirement. That is exactly the operational context annotations cannot express.

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?

Four sentences, all front-loaded and information-dense: capability first, then calendar semantics, then output/truncation behavior, then pricing. No filler, though the pricing sentence is appended without transition and packs several facts.

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?

With no output schema, the description does the heavy lifting by summarizing return fields and truncation flags, and it covers both operations, the weekend/holiday model, and payment. A full field-level return spec and pagination/count semantics are not given, leaving a small gap for a 7-parameter tool.

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 100%, so the baseline is 3, but the description adds meaning beyond the schema: it explains that the weekend mask supports non-standard weeks (Friday-Saturday, Sunday-only) and that holidays are an explicit list so nothing relies on a stale table. That is genuine semantic value for the weekend and holidays parameters.

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 specific verbs and resource ('business days calculator... add or subtract N working days... or count the working days between two dates') and immediately frames the caller-supplied calendar, which separates it from siblings like calendar_convert, dst_transitions and rrule_expand. An agent can identify the tool's job without opening the schema.

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 description distinguishes the two modes (add vs count) and notes the calendar is caller-supplied, so usage is implied, but it never names an alternative tool or states when this is the wrong choice versus recurrence or conversion tools. Implied usage only.

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