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

Annotations already declare readOnlyHint and idempotentHint, establishing a safe, repeatable operation. The description adds meaningful behavioral context beyond annotations by specifying the act/365 day-count convention and the role of the first cashflow date as the valuation base, which are not present in the structured metadata.

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 two sentences with zero wasted words. The first sentence immediately states the core purpose, and the second adds the key calculation detail. This is exemplary conciseness.

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?

Given the simple two-parameter schema, strong annotations, and presence of an output schema, the description sufficiently covers the method and usage context. It does not discuss edge cases like unordered cashflows, but that is not essential for this type of calculator.

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 input schema provides 100% description coverage for both parameters, including the meaning of dates, amounts, and annual rate units. The description adds no substantive new parameter semantics beyond restating that the rate is annual in percent, so the baseline of 3 is appropriate.

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 clearly identifies the tool as a date-aware net present value calculation with specific verb 'discounted' and resource 'cashflows'. It distinguishes itself from sibling tools like 'npv' by emphasizing fractional-year (act/365) discounting based on the first cashflow's date.

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 signals its intended use case by highlighting 'date-aware' and 'fractional years', implying suitability for irregular-dated cashflows rather than periodic ones. However, it does not explicitly name alternatives or state when not to use it, so it falls short of full when/when-not guidance.

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