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

With no annotations, the description carries the full behavioral burden and does well: it discloses the $0.005 x402 payment requirement, that it accepts height or latest/finalized/safe, and the supported chains. It doesn't cover rate limits, auth beyond x402, or error behavior, but the cost/payment disclosure is genuinely useful context not available elsewhere.

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 price then the payload contents, packed into a few dense sentences with no filler. The routing contrast is well placed after the content list, though the opening price token is slightly abrupt.

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, the description compensates by enumerating the returned fields, and it covers accepted inputs and supported chains. An agent has enough to call it correctly; only edge details like pagination or error behavior are absent.

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 67%; the schema documents chain and number, and the description reinforces these ('Accepts a height or latest/finalized/safe', lists the six chains). The x_payment parameter is undocumented in both, and the description adds no format detail beyond the schema, so baseline 3 is appropriate.

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 ('the full header of any block') and enumerates exactly what it returns: timestamp/age, transaction count, gas used vs limit with utilization and congested flag, base fee, miner and parent hash. It explicitly contrasts with the sibling chain_block_number, so an agent can distinguish them without opening either 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?

The line '/chain/block-number says WHERE the chain is; this says WHEN that block happened and how contested it was' gives a clear selection rule against the nearest alternative. It stops short of stating when-not-to-use or listing other siblings, but the core routing guidance is present.

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