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

With no annotations supplied, the description carries the full behavioral burden, and it does disclose several useful traits: days = 0 rolls a non-business start forward, skipped days are enumerated with reasons, and date defaults to today. However, it says nothing about invalid/unrecognized calendar codes, empty calendar arrays, or rate/latency characteristics for this dependency-heavy lookup.

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?

Content is front-loaded with the core operation first and supporting rules after, and every clause earns its place. The calendar-example sentence is long and read as a run-on, so a small amount of structure could be tightened without losing information.

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 three-parameter, no-output-schema calculation tool, the definition covers the operation, all parameter meanings and edge cases, calendar sourcing, and even the shape of the returned skipped-day explanation. Nothing an agent needs in order to call it correctly is missing.

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 0%, so the description must compensate, and it does: days explains sign convention and the zero edge case, date explains the today default, and calendars explains AND semantics (open in every calendar) plus concrete code examples across FX, exchange, payment-system, and bank categories plus a pointer to list_calendars.

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 description opens with a specific verb-and-resource statement: computes the date N business days after (or before, via negative days) a start date. That distinguishes it immediately from business_days_between, is_business_day, and bank_holidays, which answer different questions.

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?

It names concrete use cases (settlement/value dates, T+1/T+2, payment due dates, deadlines) and points to list_calendars for obtaining valid calendar codes. It does not explicitly say when to prefer a sibling such as is_business_day or what to do for plain holiday lookups, so it stops short of full routing guidance.

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