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

Annotations cover only readOnlyHint and openWorldHint, but the description adds genuinely useful context the annotations cannot: deterministic/no-AI behavior, per-call pricing ($0.001 USDC via x402 on Base) with a free tier, and what information comes back (holiday name, NYSE early closes, prior/next business day). That is real behavioral disclosure beyond structured fields.

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 tight sentences: the core semantics first, then determinism, then cost. Every sentence carries information, though the calendar list in the first sentence partly duplicates the schema.

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?

No output schema exists, so the description usefully enumerates what the call returns (holiday, early closes, adjacent business days) and discloses the payment model. This is close to complete for a two-parameter predicate 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% and both parameters are fully documented there, including aliases and the all-calendars-must-be-open rule. The description only restates the calendar names, adding no syntax or format detail beyond the schema. Baseline 3 applies.

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 predicate over a date and enumerates the calendars it applies to, making the operation unambiguous. It does not explicitly contrast itself with siblings like business_days_between or settlement_date, so it falls short of the top score.

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 when-to-use guidance and no mention of alternatives among the six sibling date tools. The agent must infer from the name alone whether this is the right tool versus business_days_between or settlement_date.

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