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

Goes well beyond the annotations: discloses pricing ($0.01/call via x402 USDC or card key), the 25-call free tier, that failed calls are free, and that repeated calls are not free — which concretely explains the idempotentHint=false flag. It also confirms the call reads or computes only and changes nothing, reinforcing readOnlyHint/destructiveHint=false.

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-loads identity and return values, then usage, then billing — a sensible order. It is dense and semi-colon chained, and the pricing tail is verbose, but nearly every clause carries decision-relevant information.

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 correctly enumerates the returned fields and units, so an agent knows what it gets. The only gap is the unreconciled "takes no input" claim against the optional `only` parameter, which slightly muddies an otherwise complete picture.

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% and the single optional "only" filter is fully documented in the schema, so the baseline is 3. The description adds nothing about that filter and, worse, says "Takes no input," which an agent could read as ruling out the projection parameter entirely.

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 — current gas price on Unichain — and enumerates the exact outputs (gas price, base fee, suggested priority fee in gwei, cost of a 21,000-gas transfer). It also names the sibling it is not (unichain_receipt) so an agent can separate live-price reads from historical fee lookups.

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?

Gives explicit when-to-use ("before sending a transaction or to decide whether to wait") and an explicit routing rule away from a sibling: for a past transaction's actual fee, use unichain_receipt. It also preempts the most likely misuse — repeatedly re-calling for freshness — by noting each call is charged.

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