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

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so the safety profile is covered. The description adds the genuinely useful disclosure that the result is a decimal integer rather than the hex string EVM RPC normally returns — important since there is no output schema. No mention of freshness, caching, or rate limits.

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?

One sentence, front-loaded with the resource and ending with the format detail. Zero filler and nothing left dangling.

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 single-parameter read with full annotation coverage, the return format is the one thing an agent could not infer elsewhere, and the description supplies it. The only gap is the absence of any routing guidance relative to rpc_call.

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 description coverage is 100% and the single 'chain' parameter has a documented enum of 29 slugs, so the schema carries the semantics. The description adds nothing about the parameter beyond what the schema already states, making the baseline 3 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 precise resource and scope: 'the latest block number of an EVM chain', plus the return format. The resource is specific enough that an agent can distinguish it from get_balance or rpc_call without opening a schema, though no sibling is named explicitly.

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?

No when-to-use guidance at all. With rpc_call and list_chains as siblings, the description never says why an agent should prefer this over a raw eth_blockNumber RPC call or when a chain slug is required.

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