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

Goes well beyond the annotations: it discloses the per-call price ($0.01 via x402 USDC or card key), a first-25-free tier, and that failed calls are free, which meaningfully explains the idempotentHint=false (repeats cost money). 'Reads or computes only and changes nothing' largely restates readOnlyHint/destructiveHint but reinforces it. Minor gap: no mention of how the percentile/aggregate values are computed over the window when fewer blocks exist.

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 the core capability and return shape, then usage, then commercial terms — a sensible order. The billing sentences are dense but each carries decision-relevant information; the block run-length and mixed topics keep it from a 5.

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 still fully specifies the returned fields and aggregate summary, so an agent knows what it will get. Combined with pricing, failure semantics, and the sonic_gas alternative, nothing an agent needs in order to call it correctly 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 description coverage is 100% and the single 'blocks' parameter is fully documented in the schema (5-100, default 20), which the description repeats rather than extends. The 'Example: blocks=20' adds only marginal value. Baseline 3 is appropriate when the schema already carries the parameter semantics.

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 (gas price history on Sonic via eth_feeHistory) and enumerates exactly what is returned: base fee in gwei per block, block fullness, 10th/50th/90th percentile priority fees, and low/avg/high base fee over the window. It explicitly distinguishes itself from the sibling sonic_gas ('for the current price alone use sonic_gas'), so an agent can route 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?

Gives concrete when-to-use conditions (judge whether fees are rising, pick a priority fee, time a transaction) and names the alternative (sonic_gas) with the condition that selects it. Also notes cost behavior so an agent can decide whether to call repeatedly.

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