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

With no annotations, the description carries the behavioral burden and does disclose two genuinely important traits: the $0.01 USDC-on-Base (eip155:8453) x402 cost and that payment goes in params._meta['x402/payment']. That payment/auth requirement would be invisible from the schema and is exactly the kind of context that prevents failed calls. It stops short of stating read-only nature, rate limits, or response shape, so not 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?

Pricing is stated twice in near-identical form ('$0.01 per call in USDC on Base via x402' followed by 'Price: $0.01 per call in USDC on Base (eip155:8453)'), which is pure waste. The opening sentence is a family catalogue rather than a front-loaded statement of this tool's single job, so the useful payment detail is buried.

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 3-parameter tool with full schema coverage and no output schema, the payment disclosure covers the main non-schema gap. However, the description leaves a real ambiguity unresolved: 'add N business days' versus a start/end/country schema with no count, and it never says what `add` returns (a resulting date). That mismatch is a completeness problem the schema cannot fix.

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 description coverage is 100% (end/start documented as YYYY-MM-DD, country enum documented as US federal vs UK England & Wales), so the schema already does the heavy lifting. The description adds no parameter-level semantics and in fact introduces confusion by implying an 'N' count that does not exist in the schema.

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?

The text reads as a whole-family blurb ('is a date a business day, add N business days, count business days between dates, and list a year's holidays') rather than a statement of what this specific tool does. Three of those four listed capabilities map to sibling tools (bizcal_api__day, bizcal_api__between, bizcal_api__workdays, bizcal_api__year), so the description never distinguishes `add` from its siblings. The 'add N business days' phrasing also conflicts with the schema, which takes start/end/country and has no N parameter.

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?

No when-to-use / when-not-to-use guidance is given, and the sibling tools are never named or routed to. An agent cannot tell from this text why it should pick `add` over `bizcal_api__between` or `bizcal_api__workdays`, especially given the overlapping start/end shape.

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