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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuinely useful behavioral facts: integer-exact conversion with no precision loss, pure-compute/latency-and-cost positioning, no API key requirement, and the x402/credit-token payment path. These go beyond what the annotations declare.

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?

Core purpose is front-loaded, but the body carries marketing language ('the unit-conversion commodity agents call constantly'), a 'Not financial advice' disclaimer, and detailed pricing boilerplate that dilute the signal. Functional content could be half the length.

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?

An output schema exists, so return format need not be described, and the behavior is well covered. The only gap is that from/to are optional in the schema yet the description implies all three are passed, leaving default-unit behavior unexplained.

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 100%, so the schema already documents amount/from/to, and the description's note about passing a number like 6 for USDC largely restates the schema's 'or decimals number'. It adds no format examples (e.g. how to express from/to defaults) beyond the structured fields, so the baseline 3 applies.

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 (amounts between wei/gwei/ether or arbitrary token decimals), with the supported unit ladder spelled out. It is clearly separable from siblings like fx_convert (fiat) and file_convert (files) by resource alone.

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?

It hints at context ('when building transactions') and says what to pass, but never states when to choose this over fx_convert or any other conversion utility, nor any exclusion conditions. Usage is implied rather than directed.

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