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

With no annotations, the description carries the behavioral burden, and it does disclose two useful traits: exact BigInt arithmetic for wei amounts (precision/determinism) and a per-call cost of $0.001 USDC on eip155:8453, which implies payment/auth is required. It stops short of stating it is a pure side-effect-free computation or handling error cases.

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?

Two sentences, front-loaded with the core formula before the pricing aside. Every clause contributes; nothing is padded.

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 3-param calculator with no output schema, the description conveys both the computation and the two result currencies (ETH cost and USD), which largely covers the return. It does not state the exact output fields or rounding, a minor gap for a trivial tool.

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 the baseline is 3, but the description goes further by explaining how the three inputs combine mathematically (gasUnits × gweiPrice, then × ethPriceUsd), which adds computational meaning beyond the terse schema labels.

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 (Calculate) and resource (gas fee) and spells out the exact formula (gas units × gwei price → ETH → × ETH price → USD). This unambiguously separates it from neighbors like crypto_wei_eth_converter or dev_llm_cost_calculator.

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?

No guidance on when to use this versus alternatives such as crypto_wei_eth_converter or live_exchange_rates for sourcing the ETH price. The only usage-adjacent sentence is the x402 pricing note, which is cost information, not invocation guidance.

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