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

No annotations exist, so the description must carry the full behavioral burden. It does disclose two useful traits — the result is expressed as a percentage and there is a '5 free trial calls per signed wallet' payment/quota constraint — but it says nothing about input parsing (all three params are declared as strings), edge cases like zero or negative years, or the return shape.

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?

Two short sentences, front-loaded with the operation and then the inputs, with the quota note at the end. The leading 'Cagr:' label mildly duplicates the tool name but costs little.

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 three-input calculator with no output schema this is close to adequate, since the operation and inputs are named. It still leaves out input type/unit conventions, edge-case behavior (zero or negative years, negative growth), and why no parameters are required.

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 0%, so the description must compensate, and it largely does not: it only restates that start value, end value, and years are needed. It adds no format or unit detail (are these numeric strings, decimals, fractional years?) and doesn't explain why all three parameters are marked optional.

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 ('Calculate Compound Annual Growth Rate (CAGR) as a percentage'), so an agent knows exactly what computation is performed. It does not name or distinguish itself from nearby siblings such as x402-annualized-return or x402-compound-interest, which is the only thing keeping it from a 5.

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 only implied by the sentence 'Provide start value, end value, and number of years,' which tells the agent what inputs to supply but not when this tool should be chosen over sibling growth/return calculators. There is no when-not guidance or named alternative.

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