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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely new context beyond that: the data source (Cloudflare DoH) and the batching behavior (all six records in one call, or one type via 'type'). It omits error behavior and any rate-limit caveats, which keeps it short of a 5.

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?

Two tight sentences with zero filler. The capability statement comes first and the sibling routing follows, which is the right front-loading for a selection decision.

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?

With no output schema, the description usefully states what comes back (the six record types), which is the main thing absent from structured data. Nothing critical for invoking it is missing, though response shape for the single-type case is left implicit.

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%, so both parameters are fully documented in the schema, and the schema description for 'type' already states 'Omit to get all 6 at once.' The description's mention of single-vs-all types largely repeats that, so the baseline 3 applies.

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 specific verb and resource ('Returns DNS records for a domain'), enumerates the six record types returned, and names the underlying mechanism (Cloudflare DNS-over-HTTPS). It explicitly distinguishes itself from whois_lookup and email_security, so an agent can route without opening any schema.

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?

Gives explicit alternatives with the conditions that select them: registration data -> whois_lookup, SPF/DMARC/DKIM analysis -> email_security. This is textbook when-to-use guidance tied to sibling tools.

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