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

Annotations only declare readOnly and openWorld, so the description usefully adds two behavioral facts they don't cover: exact integer arithmetic with no floating-point error, and a per-call charge of $0.002 USDC via x402 (an auth/payment requirement). It also hints at the response shape (base integer plus hex).

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?

One dense sentence front-loads the core capability, with the parameter example and cost appended. Nearly every clause earns its place, though the unit enumeration is slightly listy.

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 4-param tool with no output schema and no annotation coverage for cost, the description covers the essentials (exactness, payment, return shape) but omits what happens when `to` is omitted (only `value` is required), error behavior on unknown units, and any limits on precision/decimals.

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 0%, so the description carries the full parameter burden. It partially compensates by explaining `from` as a unit and `decimals` as the token precision with a concrete example, but `to` and `value` are never described, and no accepted enum values for the unit parameters are listed.

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 gives a specific verb+resource (exact crypto unit conversion) and enumerates the concrete unit families it handles (wei/gwei/ether, lamports/SOL, sats/BTC, USDC base units, arbitrary token decimals). It does not, however, differentiate itself from near-neighbor siblings such as `convert`, `calc`, or `fx`, so an agent must infer the boundary.

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 implied through examples ('or any token decimals (from=units&decimals=8)') and the cost note, but there is no explicit when-to-use/when-not statement nor any named alternative (e.g. `convert` for non-crypto units). The agent is left to infer the routing.

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