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

Beyond the annotations it discloses the cost model ($0.01/call, first 25 free, failed calls free) and explicitly notes 'each call is charged, so repeats are not free,' which explains the non-obvious idempotentHint=false. It also restates that the call 'reads or computes only and changes nothing,' reinforcing the destructiveHint=false profile with plain-language confirmation.

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?

The main capability and its outputs are front-loaded, followed by usage guidance, an example, then pricing. It is dense but almost every clause carries information; the pricing/payment-key sentence is the longest and could be tightened slightly without losing value.

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?

There is no output schema, but the description enumerates the returned fields (base fee, fullness, percentile priority fees, window summary), so an agent knows what comes back. For a single-optional-parameter read tool with full annotation coverage, nothing material 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?

Schema coverage is 100% and the schema already documents blocks as 'How many recent blocks, 5-100 (default 20)'; the description repeats the same range and default and adds an example (blocks=20). It is consistent but contributes essentially no meaning beyond the structured field.

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 names a specific verb and resource ('Gas price history on Ethereum') and enumerates the exact outputs: base fee per block, block fullness, 10th/50th/90th percentile priority fees, and low/average/high base fee over the window. It also distinguishes itself from the closest sibling by stating 'for the current price alone use eth_gas.'

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 three concrete use cases ('judge whether fees are rising, pick a priority fee or time a transaction') and an explicit exclusion routing to eth_gas for the current price. An agent does not need to infer when to pick this tool over its sibling.

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