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

Annotations already cover the read-only/idempotent/non-destructive profile, so the bar is lower. The description adds genuinely non-obvious behavior: the pruned-history boundary (blocks older than height 15,500,000 return an error, not an empty block), which prevents an agent from misreading a failure as absence of data.

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-loaded with the core purpose, then cleanly segmented into when-to-use, when-not-to-use, returns, and boundary. The returns list is long but earns its place given there is no output schema; a minor amount of enumerative bulk.

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 and no required params, the description compensates by enumerating every returned field and disclosing the historical retention boundary and the hash-precedence behavior. An agent has everything needed to call it and interpret the result.

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 both params including the hash-takes-precedence rule. The description's 'number, tag (latest/finalized/safe) or hash' restates the schema's enum-like tags without adding syntax or edge cases beyond the pruned-height note.

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 ('One Ethereum block by number, tag or hash') and enumerates the fields returned, which pins down exactly what the tool is. It explicitly distinguishes itself from the nearest siblings, eth_get_transaction and eth_get_fee_rates.

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?

Contains explicit 'When to use' scenarios (block fullness, production time, base fee, builder) and explicit 'Do not use' exclusions that route the agent to the correct sibling tools. This is the when/when-not/alternatives pattern at full strength.

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