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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description reinforces this with 'reads or computes only and changes nothing'. It adds genuinely non-obvious behavior that annotations cannot express: per-call cost ($0.01 via x402 USDC or card key), the first 25 free, failed calls free, and that repeated calls are charged - which is consistent with idempotentHint=false rather than contradicting it. It stops short of stating rate limits or latency, so not a 5.

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?

Everything is front-loaded: purpose and output shape first, then the sibling disambiguation, then pricing. The pricing and free-tier sentence is lengthy but each clause carries decision-relevant information for cost-aware callers, so there is no padding to cut.

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 returns, and it does so specifically: base fee in gwei per block, block fullness, 10th/50th/90th percentile priority fees, and low/average/high base fee over the window. Together with the cost model and safety hints, an agent has everything needed to call this correctly.

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 parameter is already documented as 5-100 with default 20, so the description's restatement adds little. The one extra contribution is a concrete usage example ('blocks=20'), but no format or edge-case guidance (e.g. what happens outside the ranges) is added beyond the schema.

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 opens with a specific verb and resource ('Gas price history on Gnosis (eth_feeHistory)') and explicitly scopes itself to a window of blocks, naming the underlying RPC. It also names the sibling it is not ('for the current price alone use gnosis_gas'), so an agent can distinguish it from gnosis_gas without opening either 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?

It gives explicit when-to-use guidance ('judge whether fees are rising, pick a priority fee or time a transaction') and an explicit alternative with its selection condition ('for the current price alone use gnosis_gas'). Nothing about choosing between this and its sibling is left to inference.

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