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

With no annotations, the description carries the full behavioral burden. It usefully discloses a payment requirement (x402, $0.001/call in USDC on eip155:8453), which is real context an agent needs. However it says nothing about edge cases (zero/negative values or years), whether the result is a decimal or percentage, or failure behavior for invalid inputs.

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?

Front-loaded formula statement followed by the pricing note in a single compact block, with no filler. The em-dash-joined pricing clause is slightly awkward but costs almost nothing.

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 three-param math tool with no output schema and no annotations, the definition covers inputs and cost but omits the return format (percentage vs. decimal) and edge-case behavior. Adequate but with a clear gap for an agent that must interpret the result.

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%, so all three parameters (initial, final, years) are already documented in the schema. The description restates the same three inputs without adding units, sign conventions, or expected ranges. Baseline 3 is appropriate when the schema does the work.

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?

Names a specific metric (compound annual growth rate) and gives the exact framing — initial value, final value, number of years — which is precise enough to distinguish it from a generic interest calculator. It does not explicitly route against its closest siblings (compound_interest_calculator, roi_calculator), so it falls short of 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?

There is no when-to-use or when-not-to-use guidance, and no alternative tool is named. 'The standard way to annualize returns' implies the use case but leaves the agent to infer that compound_interest_calculator or roi_calculator are the wrong choice.

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