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

With no annotations, the description carries the full load and does reasonably well: it discloses the payment model (paid per call, x402 on Base), the sort order, the tier set, and that prices are current. It omits what happens on missing/unpaid payment and any rate limits or data freshness caveats.

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 tight sentences: the core output description is front-loaded and the pricing note is appended last. Every clause carries information (chains, sort order, tiers, price, payment rail) with no filler.

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 and no annotations, the description still conveys the return shape (USD cost per chain, sorted, three speed tiers) and the payment requirement. Only edge details such as failure behavior or data-freshness policy are missing, which is a minor gap for a read-only single-parameter 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 description coverage is 100% and the schema already documents the gas parameter's range (21000-30000000) and default (65000). The description only restates 'given gas units', adding no unit conventions or guidance on choosing values, so the baseline holds.

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: computes USD cost of a transaction across six named chains, sorted cheapest first, with slow/standard/fast tiers. This is clearly distinguishable from a single-chain gas lookup like gas_now without needing the 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?

The description implies usage ('given gas units', the chain list, the tier breakdown) but never states when to pick this over sibling gas_now or other cost tools, nor any prerequisites. The one explicit contextual fact is the per-call price of $0.002 USDC paid via x402 on Base.

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