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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the description need not repeat safety. It adds useful behavioral context: data comes from a public node, the call costs a fixed amount, and the response is byte-identical to a REST endpoint.

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?

Three compact sentences, each earning its place: the purpose and liveness use case, the cost, and the supported chains plus REST equivalence. It is front-loaded and has 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 one-parameter read-only tool with an output schema and strong annotations, this is complete. The agent knows what the tool does, when to choose it, how much it costs, which chains are supported, and how it maps to a REST endpoint.

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%, so the schema already fully documents the single required chain parameter. The description adds value by listing the supported chain keys in prose and restating that exactly one chain is queried, but this mostly duplicates the schema's parameter description.

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 and resource: returns the latest block number for one chain. It also distinguishes itself from the many chain_* siblings by framing it as the cheapest liveness/height check and noting it is byte-identical to a specific GET endpoint.

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?

Explicitly says when to use it: as a cheap 'is the chain alive and where is it' check, with a concrete $0.001 USDC cost. It does not name alternative tools to prefer for deeper block data, but the 'one chain' and 'cheapest possible' framing gives clear context.

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