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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds genuinely new behavioral facts beyond the annotations: the call is paid ($0.005 USDC on Base via x402), which materially affects invocation decisions, and it lists the returned fields for a tool with no output schema.

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 sentences, front-loaded with the payload contents and closing with the payment cost, which is the highest-risk fact for an agent. The long enumeration in sentence one is dense but every item earns its place by describing a return field.

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 burden of describing return values and does so field by field, plus the payment requirement, and the sole parameter is fully documented in the schema. Nothing essential for correct invocation is missing for a simple read-only snapshot 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 coverage is 100% for the single optional gasLimit parameter, including its pattern and the note that it adds estimatedCost.custom in ETH and USD. The description adds no parameter meaning of its own, so baseline 3 is appropriate when the schema does the full job.

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 artifact ('Base gas snapshot') and enumerates exactly what it contains: gas price, base fee, priority fee, 10-block base-fee trend, ETH/USD, and estimated USD costs for four transaction types. That enumeration clearly separates it from siblings like base_token_price or base_balance, so an agent can pick it without opening 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?

'right now' implies this is for current, point-in-time gas estimation rather than historical lookups, which is useful context. However, it never names an alternative or states when not to use it (e.g., use base_token_price for pure price data), so the routing guidance is implied rather than explicit.

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