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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description still adds real value: revert behavior (422 with reason, uncharged), the billing model ($0.01/call, 25 free, failed calls free) and the non-idempotent cost note that explains idempotentHint=false. It does not mention latency or which errors besides revert can occur, so a 4 rather than a 5.

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?

Purpose, inputs, alternatives, error behavior and pricing are front-loaded in that order with no filler. The pricing/credits sentence is the longest and is arguably the least essential, but it justifies the non-idempotent annotation so it still earns its 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 states the returned quantities (gas units, gwei, ETH) and cost basis, plus the failure mode and the fact that nothing is mutated or persisted. An agent has everything needed to call it correctly and interpret the result.

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%, so baseline is 3. The description goes modestly beyond it by framing value as ETH and telling the agent to supply sender only 'when the call depends on it', which is a usage hint the schema's '(default: an empty address)' does not convey.

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 and resource ('Estimate the gas a transaction would use on Base') plus the underlying RPC method (eth_estimateGas) and the return units (gas, gwei, ETH). It explicitly distinguishes itself from base_gas, which only returns the gas price, so an agent can pick between the two 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?

'Use before sending a transaction or to price a batch' gives positive trigger contexts, and 'for the gas price alone use base_gas' names the alternative and the condition selecting it. Both when-to-use and when-to-use-something-else are covered.

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