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

Annotations already declare read-only/idempotent/non-destructive, and the description adds substantial context beyond them: no EIP-1559 base fee, the exact cost formula, the estimator's block horizons, the meaning of "legacy_fallback": true when data is scarce, and the availability of 21,000-gas transfer costs in LAX. This is real behavioral disclosure an agent cannot get from the annotations.

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 core answer (current fee levels in wei/gwei) before the formula and estimator detail. It is dense and somewhat run-on, but with no output schema most of this detail 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 carries the full burden of explaining return values, and it does so thoroughly: node eth_gasPrice, per-horizon smart-fee estimates with success rates, the legacy_fallback flag, and derived transfer costs. Nothing an agent needs to interpret the result 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 no parameters, so there is nothing for the description to disambiguate and the baseline is 4. The description spends its space on return semantics instead, which is a reasonable use of a zero-param definition.

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?

The description states a specific resource and unit (current fee levels in wei and gwei) and explains the fee model (gas used × gas price, all to the miner). It is clear what the tool returns, though it never explicitly names its closest sibling, estimate_gas, so an agent must infer the distinction between 'current chain fee levels' and 'estimate for a specific call'.

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?

Usage is implied rather than stated: the description makes clear this is a snapshot of current fee levels, but it gives no explicit when-to-use or when-not, and no guidance on choosing it over estimate_gas or block_reward. Adequate but with a clear gap.

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