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

The annotations already declare read-only, idempotent, non-destructive, open-world behavior, so the description does not need to repeat safety traits. It adds useful behavioral context by disclosing the exact calculation model and a cost of 1 credit, though it does not discuss rounding or return-format details.

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 compact sentences with the core calculation front-loaded and the formula immediately available. The cost note is brief and useful, with no wasted wording.

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?

This is a simple three-parameter calculator with full schema coverage and annotations covering safety behavior, so the definition is nearly complete. A little more detail on the expected return value or rate convention would make it fully self-contained.

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%, so all three parameters are already documented in the input schema. The description adds the formula mapping between present value, annual interest rate, and years, but does not add much beyond what the schema already explains about parameter 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 states a specific verb and resource: calculating an investment's future value, and gives the exact compound-interest formula. It is clear what the tool computes, but it does not explicitly distinguish itself from nearby siblings such as compound_interest or calculate_investment_return.

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?

Usage is implied by the specific formula and output type, so an agent can infer this is the tool for future value with annual compounding. However, there is no explicit when-to-use guidance, no exclusions, and no routing to similar financial calculation siblings.

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