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

Annotations already declare readOnlyHint=true and openWorldHint=true, but the description adds crucial behavior beyond them: public-RPC estimate limits, typical gas-unit assumptions, no future-fee guarantee, sub-second latency, output shape, and a pay-per-call model (0.06 USDC via x402). These are exactly the details an agent needs to decide whether and how to invoke it.

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?

The purpose and operational limits are front-loaded, but the description is padded with token-support disclosure, ERC-8004/ACP identity verification, payout-wallet addresses, and 'not financial advice' boilerplate that do not help an agent select or invoke the tool. Several sentences do not earn their place.

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?

With no output schema, the description carries the return-value burden and does so: ranking, per-chain gwei and USD, and a timing read. It also covers inputs, defaults, latency, cost, and estimation limits, leaving no material gap for an agent to call it correctly.

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%, and both parameters are enum-documented with defaults. The description only restates that tx_type and chains are optional and repeats the example already present in the schema, so it adds little beyond structured data.

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 states a specific verb and resource: 'live fee estimate in USD for an ETH transfer, ERC-20 transfer or DEX swap' across four named chains, plus cheapest-chain ranking and 7-hour comparison. No sibling tool does gas-fee estimation, so the purpose is unmistakable from the first sentence.

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 gives a clear when-to-use context: 'For anyone about to send or swap.' There are no explicit exclusions or named alternatives, but because no sibling tool overlaps this function, the absence of alternatives is less costly.

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