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

With no annotations, the description carries the full behavioral burden. It does disclose a non-obvious operational trait — the x402 pay-per-call price ($0.001 USDC on eip155:8453) — which an agent needs before invoking. It says nothing about precision, rounding, invalid-unit handling, or the return value, which for a conversion tool is a moderate but tolerable gap given the operation is stateless and non-destructive.

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 compact sentences, with the core purpose front-loaded before the ancillary pricing detail. The unit list is a slightly dense run-on, but nothing is wasted.

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-parameter, no-output-schema converter the description is close to sufficient, but it omits the return shape (a single numeric value) and whether errors occur for unsupported units. Given zero annotation coverage and placeholder schema descriptions, a bit more disclosure would be warranted.

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 nominally 100%, but the actual descriptions are placeholder-level ("To", "From", "Value"), so the schema conveys almost no meaning. The description partially compensates by mapping human-readable unit names to enum codes (hectares→ha, acres→acre, square miles→mi2), but the mapping is incomplete and the mm2 mismatch leaves one gap.

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 ("Convert") and resource (area units) and enumerates the unit set, so an agent can tell it apart from the sibling length/volume/weight converters at a glance. However, the enumerated units do not fully match the schema enum: "square millimeters" (mm2) is listed but absent from the enum, while the enum's cm2 is described only as "centimeters," creating a small ambiguity about scope.

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?

No when-to-use guidance, no prerequisites, and no mention of how this differs from or relates to the many sibling converters. The only additional context is a pricing note, which is not usage guidance.

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