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

Annotations already declare read-only, idempotent, and non-destructive behavior, so the safety profile is covered. The description states the additive behavior and that it returns a business day, but it does not disclose the definition of 'business day' (e.g., weekends and US holidays), how non-business-day start dates are treated, or whether negative day counts are supported. No contradiction with annotations exists.

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?

The description is a single direct sentence with no filler, and the core operation is front-loaded. It is appropriately concise, though slightly too terse to include the US-holiday context and output format details.

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 simple two-parameter tool, the description is close to sufficient: the schema covers the date format and the description covers the operation. But with no output schema, it does not state the output date format, and it leaves the exact business-day calendar ambiguous, so an agent must make reasonable assumptions.

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?

The schema already documents the date format, and the description maps the days parameter to 'N business days', giving it basic semantic meaning. However, it does not specify constraints such as negative values, zero, maximum size, or how a non-business-day start date is handled, so the description only partially compensates for the schema's 50% coverage.

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 uses a specific verb and resource: 'Add N business days to a date' and states the return value, making the core operation clear. It does not explicitly distinguish itself from siblings like calendar_is_business_day or calendar_holidays, but 'add' is unambiguous enough that an agent can identify when it applies.

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 guidance on when to use this tool over related siblings such as calendar_is_business_day or calendar_holidays. It also does not mention use cases, prerequisites, or exclusions, leaving the agent to infer when this is the right tool.

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