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

Annotations already declare read-only, idempotent, non-destructive behavior. The description adds genuinely useful context beyond annotations: data comes from public RPCs and each call costs $0.001 USDC via x402, which materially affects invocation decisions.

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 no filler. The output data and supported chains are front-loaded, followed by the usage context and cost disclosure.

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 one-parameter, read-only tool with no output schema, the description covers the key return fields, source, chain scope, and cost. The main omission is default behavior for omitted parameters, but this is minor given the schema's clear enum.

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?

The description names the supported chains, which maps to the `chains` array enum, but it does not explain default behavior when the parameter is omitted or whether one or both chains can be requested. With 0% schema description coverage, this is only partial compensation.

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 exactly what is returned (gas price, base fee, block height) and for which chains (Base and Arbitrum), which makes it immediately distinct from generic chain fee tools. The purpose is concrete and actionable.

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?

Provides a clear use case ('what a transaction costs before you send it') that tells an agent when to consult this tool. It does not explicitly name alternatives or exclusion criteria, so it stops short of full 5-level guidance.

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