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

Annotations already declare readOnlyHint and idempotentHint, and the description adds significant behavioral detail: it resolves no wallet, is free on both meters, consumes no rate limit, works even with zero balance, counts are refreshed daily, and as_of indicates when they were taken. This far exceeds the annotation coverage and fully explains the tool's side effects and data freshness.

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?

The description is structured: purpose front-loaded, then cost details, then explanation of the numbers. It is a bit verbose with the cost paragraph, but every sentence adds value whether clarifying cost, data freshness, or interpretation. It is not overly long for the information provided.

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?

Without an output schema, the description carries the burden of explaining what the tool returns. It does so clearly: the two numbers, their relationship, the larger share for bare addresses, the refresh cadence, and the as_of field. An agent has everything needed to interpret the result and decide on subsequent actions.

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 tool has no parameters, so the description cannot add parameter specifics. The baseline for zero params is 4, and the description compensates by explaining the response fields (addresses_with_an_identity, addresses_checked, as_of) and their meaning, which is more than expected.

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 states exactly what the tool does: reports how much of the index carries each identity type, and context for evaluating whether a lookup is worthwhile. It clearly distinguishes this from sibling tools (which resolve wallets or check balances) by focusing on coverage statistics.

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 description explicitly says to use this tool before making a lookup to judge if it's worth it. It also notes the tool is free and consumes no rate limit, guiding when to call it. It does not explicitly name alternative tools for when not to use it, but the purpose and cost context make usage clear.

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