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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false, so the safety profile is covered. The description adds the behavioral assumption of a 'steady yearly rate' and shows an example output, but does not describe return format beyond the example, precision, or any edge cases.

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 front-loaded with the core definition and an example, followed by a brief use case and a URL. It is appropriately sized, though the web page URL is marginally extraneous for tool invocation.

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, read-only calculator with full schema coverage and annotations, the description is nearly complete. It provides an example output to compensate for the lack of an output schema, though it stops short of explaining return precision or interpretation.

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%, with each parameter clearly defined in the schema itself. The description's example implicitly maps to begin, end, and years, but adds no syntax or semantic detail beyond what the schema already provides.

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 calculation (CAGR) and defines it as the steady yearly rate between two values, with a concrete example. It is clear what the tool computes, but it does not explicitly distinguish itself from related sibling calculators like compound_interest_calculator or roi_calculator.

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 gives implied usage contexts ('investments, revenue or users') but provides no explicit when-to-use vs when-not-to-use guidance or alternatives. An agent must infer that this is for steady growth rates rather than other financial calculations.

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