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

Adds real behavioral context beyond the annotations: the $0.001 USDC-on-Base cost and x402 payment mechanism, which is critical for an agent to know before calling. The only tension is that readOnlyHint=false for what reads as a pure reader, but the description's payment disclosure plausibly accounts for the non-read-only flag, so this is a mild tension rather than a contradiction.

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?

Three tight sentences, front-loaded with the returned payload, then the use case, then the cost. Every sentence carries distinct information with no repetition.

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 zero-parameter tool with no output schema, the description covers the essentials: what is returned, in what units, the practical interpretation (transfer cost), when to call it, and the billing model. Nothing an agent needs to invoke it correctly is missing.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; baseline is 4. The description adds return-shape context (units in gwei, transfer cost at 21,000 gas) that is useful even though it concerns output rather than input.

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 resource (current gas on Optimism) and exactly what is returned: gas price, base fee, suggested priority fee in gwei, plus the cost of a 21,000-gas ETH transfer. The network naming cleanly disambiguates it from the many sibling gas tools (eth_gas, base_gas, arb_gas, polygon_gas).

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?

Explicitly says when to use it: 'before sending a transaction or to decide whether to wait.' That is a clear contextual trigger, though it does not name an alternative tool or state any exclusion, so it stops short of full routing guidance.

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