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

Goes well beyond the readOnly/openWorld/idempotent annotations by disclosing commercial and rate-limit behavior: $0.01/call via x402 USDC or card key, first 25 free, failed calls free, and that repeats are charged (consistent with idempotentHint=false). It also confirms 'reads or computes only and changes nothing,' and gives return units (gwei) and a concrete real-world derivation (21,000 gas).

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?

Front-loaded with the purpose and unit-bearing payload, then use case, then pricing. Dense but mostly earns its place; the pricing sentence is a long run-on and 'Reads or computes only and changes nothing' partly restates the readOnly annotation.

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?

No output schema exists, and the description compensates by enumerating return fields (gas price, base fee, suggested priority fee in gwei, 21,000-gas transfer cost). An agent has enough to call it and interpret the answer without further information.

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 100% and the single `only` filter is fully documented in the schema, so the baseline of 3 applies. The description does not explain `only` at all and in fact says 'Takes no input,' which is mildly misleading for an agent that could shrink responses with only=price,base_fee.

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 the specific resource and payload: 'Current gas price on Ethereum (eth_gasPrice): gas price, base fee and suggested priority fee in gwei, plus what a plain ETH transfer (21,000 gas) costs.' It also names the sibling it is not (eth_receipt), so an agent can distinguish it from the past-fee tools without opening a schema.

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?

Explicit routing: 'Use before sending a transaction or to decide whether to wait; for the fee a past transaction actually paid use eth_receipt.' Both the when-to-use condition and the alternative are stated, leaving nothing to inference.

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