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

Annotations cover read-only/non-destructive, and the description adds commercially critical behavior annotations cannot: $0.01/call via x402 USDC or card key, first 25 free, failed calls free, and that repeats are charged (which coherently explains the unusual idempotentHint=false for a read). It also makes clear the tool reads/computes only and changes nothing.

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 what the tool returns, then routing, then cost. Dense but every clause carries information; the pricing sentences are long but justified because cost-per-call changes agent behavior.

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 compensates by enumerating the returned fields and the derived 21,000-gas cost figure. Combined with pricing and the sibling cross-reference, 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 description coverage is 100% and the single optional `only` projection parameter is fully documented in the schema, so the baseline is 3. The description's "Takes no input" is a slight overstatement given the optional `only` filter exists, but as a statement about required arguments it is not materially misleading.

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+resource (current gas price on Sonic via eth_gasPrice) and enumerates exactly what is returned: gas price, base fee, suggested priority fee in gwei, and the cost of a 21,000-gas transfer. It explicitly names sonic_receipt as the tool for historical fees, separating it from the many sibling *_gas and *_gas_history tools.

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 decide whether to wait" gives the triggering condition, and "for the fee a past transaction actually paid use sonic_receipt" names the alternative and the condition that selects it. Nothing is left to inference.

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