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

Annotations already declare readOnlyHint, destructiveHint=false, openWorldHint and idempotentHint=false; the description reinforces this with 'reads or computes only and changes nothing' and explains the non-idempotency economically ('each call is charged, so repeats are not free'). It also discloses the 404-on-missing-block behavior and pricing/auth (x402 USDC, card key, first 25 free, failed calls free), which is real context beyond the annotations. Slightly repetitive of the annotation hints, but valuable.

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 what is returned, then routes to the alternative, then edge cases and pricing. Dense but mostly earns its space; the pricing/auth sentence is long and slightly runs together with the read-only statement, and 'reads or computes only and changes nothing' duplicates the annotation hints.

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?

One optional param, no output schema, and the description covers return fields, missing-block behavior, billing/auth, and mutation semantics. An agent has everything needed to call it correctly and interpret failures.

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 'number' param is already documented with its 'latest' default, so the baseline is 3. The description adds format meaning ('any block by decimal number') and a concrete example (number=latest), which reduces misuse risk for the numeric case.

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+resource: latest HyperEVM block number and details, or any block by decimal number, and enumerates returned fields (hash, timestamp, tx count, gas used/limit, base fee, producer). It also names the sibling it is not (hyperevm_gas) so the agent can separate it from other hyperevm_* tools without opening a 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 explicit when-to-use ('timestamps and confirmation counts') and when-not ('for current fees use hyperevm_gas'), plus operational guidance that a not-yet-existing block returns 404 uncharged. The agent knows both the selection condition and the alternative.

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