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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds meaningful behavioral context by enumerating the exact return fields (header timestamp, transaction count, gas use, fees, roots, confirmations, head-distance evidence), which is not present in annotations.

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?

A single, front-loaded sentence that efficiently communicates purpose, input methods, and return contents without redundancy. Every phrase contributes essential information.

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 only two optional, well-documented parameters, annotations covering safety, and an output schema present, the description is complete. It additionally previews return fields, making the tool's behavior fully predictable for an agent.

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 both parameters have detailed descriptions including the precedence rule (block_number takes precedence over block_tag). The description does not add substantial meaning beyond the schema, so the baseline score of 3 applies.

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 uses a specific verb ('Get and inspect') and clearly names the resource ('one historical Base mainnet block'), with explicit input modes (exact number or latest/safe/finalized tag). It lists detailed output fields, distinguishing it from sibling tools focused on transactions, accounts, or network status.

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?

The description provides clear context for when to use the tool: block-level inspection by exact number or tag. It does not explicitly name alternatives or state when not to use it, but the tool's niche is evident from the resource and returned data, making the scope clear.

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