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

Annotations already establish the operation is read-only and idempotent. The description adds a non-obvious behavioral guarantee: it is preflighted to avoid payment during an RPC outage, which is useful cost/safety context. There is nothing that contradicts the 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?

Two short sentences with no filler. The first sentence front-loads the output fields and scope, and the second adds risk-relevant behavior. Every phrase earns its place.

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 one optional, fully documented parameter, an output schema, and read-only/idempotent annotations, the description covers the essentials: what is returned, the default, and a unique behavioral safeguard. It is complete enough for an agent to invoke correctly, though 'Base' might benefit from explicit clarification as the network name, keeping this at a 4 rather than 5.

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?

The sole parameter block is 100% covered in the schema, including formats and default 'latest.' The description's 'Latest (or specified)' restates the default without adding syntax or semantic detail, so the baseline 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?

Description clearly identifies the resource returned (Base block header) and lists its fields (number, timestamp, transaction count, base fee), which distinguishes it from sibling tools that check balances, transactions, or formats. It lacks an explicit verb like 'retrieve' or 'fetch,' and does not mention alternatives, so it is clear but not maximally differentiated.

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 no guidance on when to choose this tool over alternatives, nor any exclusions or side-by-side comparisons with siblings. The only hint is that it can return specified or latest block info, which is self-evident. This is a minimal-viability omission.

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