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

With no annotations, the description carries the behavioral burden and usefully discloses the $0.001 per-call cost plus the returned fields. It does not explicitly state read-only behavior, permissions, or rate limits, though the 'block header' framing strongly implies a read operation.

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 compact sentence front-loads pricing and then states the resource, selection mode, and returned fields. Every element earns its place with no filler.

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?

For a low-complexity, two-parameter read tool with full schema coverage and no output schema, the description gives enough return-value context to call it correctly. It is slightly incomplete because it does not distinguish this tool from related siblings.

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 schema already has 100% description coverage for both parameters, including the 'latest' default and network default. The description reinforces that the tool works by number or latest, but adds no syntax or format detail beyond the schema.

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 clearly identifies the resource as a block header and states the two selection modes: by number or latest. It also lists key returned fields, which helps distinguish it from a mere block-number lookup. It stops short of explicitly naming sibling alternatives such as chain_block_number.

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?

It implies the tool is for retrieving block-header details, but gives no explicit when-to-use guidance or exclusions. It does not tell the agent when to choose chain_block over siblings like chain_block_number or chain_gas.

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