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

Annotations already establish read-only, idempotent, non-destructive behavior. The description adds valuable behavioral context beyond that: the daily snapshot cadence, the exact probe time (11:11:11 UTC), and the fact that the board does not move intraday. It does not detail the output structure, but the listed fields and summary mention cover the main behavioral expectations.

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 well-structured sentences with no filler. The core purpose is front-loaded, snapshot behavior is explained, invocation is described, and the alternative tool is named at the end. Every sentence earns its place.

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 tool with one optional parameter, strong read-only/idempotent annotations, and no output schema, the description is complete. It explains the data scope, the temporal snapshot semantics, how to request a subset, and when to use a different tool. Nothing essential is missing for correct invocation.

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 input schema already documents the single optional domain parameter at 100% coverage. The description reinforces the same semantics by saying to ask for one domain to get its row or omit it for the board, but it does not add meaningfully new parameter details beyond what the schema already provides.

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 clearly states a specific verb and resource: it provides DNS health data for the top 100 domains from a daily snapshot, listing the exact fields (rcode, addresses, DNSSEC, nameservers, rank movement). It also distinguishes itself from the real-time sibling check_domain, so an agent can select it without opening schemas.

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 explains when to use this tool versus the alternative: use check_domain for a current check, and top_domains for snapshot-based data. It also gives practical invocation guidance: provide a domain for a single row, or omit it for the full board and summary.

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