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

With no annotations and no output schema, the description carries the full behavioral burden. It does disclose the key behavioral trait that the result is 'a percentage,' which the schema does not. It says nothing about edge cases (zero/negative years, negative or zero start values) or determinism, but for a pure calculator this is a minor gap.

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, instruction front-loaded, no padding. The leading 'Cagr:' label is slightly redundant with the tool name, which keeps it just short of ideal.

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, side-effect-free three-parameter calculator with no output schema, the description covers what it computes, the meaning of each input, and the output unit. Only edge-case behavior is unaddressed, which is a small gap for this tool class.

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 coverage is 100%, but the schema descriptions are near-useless tautologies ('End to process', 'Start to process', 'Years to process'). The description meaningfully compensates by mapping them to 'start value', 'end value', and 'number of years', which is genuine semantic value beyond the schema.

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?

States a specific verb and resource: 'Calculate Compound Annual Growth Rate (CAGR) as a percentage.' An agent immediately knows what the tool computes and the output unit. It does not, however, distinguish itself from financial siblings such as x402-compound-interest, x402-annualized-return, or x402-doubling-time, which an agent could plausibly confuse it with.

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?

'Provide start value, end value, and number of years' is input instruction, not usage guidance. The description never says when to choose CAGR over sibling growth/return tools, nor any exclusion or prerequisite (e.g. positive start value, non-zero years). Context is only implied by the math term.

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