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

Annotations already declare readOnlyHint and idempotentHint, covering the safety profile. The description adds useful behavioral context about cashflow timing (index 0 today, negative outflows) and per-period discounting, but does not disclose edge cases, output details, or special conditions. It does not contradict annotations.

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 concise sentence that front-loads the core purpose ('Net present value of a cashflow series') and adds a parenthetical with essential conventions. Every word earns its place, with no redundancy.

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 low complexity, 100% schema coverage, output schema, and strong annotations, the description adequately covers the conceptual core. It explains the cashflow convention and per-period rate, though it lacks reference to alternative sibling tools for irregular cashflows, which prevents a perfect score.

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% for both parameters, so the schema already fully explains cashflows and discountRatePct. The description's mention of index 0 and negative outflows simply duplicates the schema's cashflows description, adding no additional meaning.

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 states the tool computes the net present value of a cashflow series. It specifies key conventions (index 0 is today, outflows negative, per-period discount rate) that help distinguish it from similar tools like xnpv (irregular periods) or present-value (single cashflow).

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 explicit guidance on when to use this tool versus alternatives is provided. The phrase 'per-period rate' implies regular periods but does not mention xnpv for irregular cashflows or give any when/not-to-use context.

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