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

Goes well beyond the readOnlyHint/openWorldHint annotations by disclosing the data source, the important caveat that Gini covers only the top 100 balances rather than all holders, and a per-call cost of $0.002 in USDC via x402 with failures not charged. That cost/auth context is genuinely useful for an agent deciding whether to call. It stops short of noting rate limits or freshness/latency of the Blockscout data.

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 dense sentences, front-loaded with exactly what is returned, then caveats, then pricing. Every clause carries information, though the pricing/payment-parenthetical is packed tightly enough to slow reading slightly.

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?

An output schema exists so return shape needn't be described, and annotations cover the safety profile. What remains — data source, chain restriction, Gini scope caveat, and pay-per-call cost — is all present, so an agent has what it needs to call correctly.

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% and the single address parameter is fully documented as a 0x + 40 hex ERC-20 contract on Ethereum mainnet. The description only reinforces the mainnet restriction and adds no format or validation detail beyond the schema, so the 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?

Names a specific resource and metric set: ERC-20 holder concentration from Blockscout, enumerating top-100 share, top-10 share, and Gini coefficient. No sibling tool computes holder concentration, so the boundary is clear from the description alone.

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 states the hard scope constraint ('Ethereum mainnet only'), which tells the agent when the tool is valid, but gives no explicit when-to-use or when-to-prefer-something-else guidance. With no true sibling offering the same metric, the missing exclusions are low-cost, leaving usage implied rather than spelled out.

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