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

The description adds substantial behavioral detail beyond the annotations: it is free on both meters, resolves no wallet, consumes no rate limit, works even with zero balance, and returns daily-refreshed counts rather than live data. It also explains the coverage rate formula and why the second number is larger. The 'asking twice in a day returns the same numbers' detail aligns with the idempotentHint annotation.

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 appropriately sized for a simple no-parameter tool. Every sentence earns its place: purpose, cost/rate-limit behavior, and interpretation of the returned numbers are all covered without redundancy. The purpose is front-loaded, and the explanation of the coverage rate is clear.

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 zero-parameter tool with no output schema and strong annotations, the description is complete. It covers what the tool measures, how to use it, what the numbers mean, freshness behavior, and cost/rate-limit implications. An agent has everything needed to decide whether to call it and how to interpret the result.

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 zero parameters and the schema coverage is trivially 100%, so the baseline for parameter semantics is 4. The description does not need to explain parameters, and instead clarifies the meaning of the returned fields (addresses_with_an_identity, addresses_checked, as_of), adding value beyond the schema.

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 reports ('How much of the index carries each identity type') and its purpose ('judge whether a lookup is worth making before making it'). This clearly distinguishes it from sibling tools like resolve_wallets or account_balance, which perform actual lookups or balance reads.

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 when to use it: before making a lookup, to judge whether the lookup is worthwhile. It also provides practical context about cost and rate limits. It does not explicitly discuss when not to use it or name alternatives, but the usage context is clear.

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