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

Annotations already declare readOnly, idempotent, open-world, non-destructive, so the safety profile is covered. The description adds real behavioral context beyond that: ALL expands to a defined set of record types, and an IP input silently switches to a PTR reverse lookup. No output format or failure behavior is described, hence not 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?

Three short sentences, front-loaded with the verb and resource, then the default behavior, then the IP special case. No filler and nothing redundant with the schema.

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 two-parameter read-only lookup with no output schema, the description covers the essential call semantics: what to pass, what the default does, and the reverse-lookup edge case. It stops short of describing result shape or the enum types not covered by ALL, but nothing critical to correct invocation is missing.

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 baseline is 3, but the description adds meaning the schema does not: it defines ALL as a query of A, AAAA, CNAME, MX, NS, TXT, SOA and CAA, and explains that an IP-valued name produces a PTR lookup. Note it does not account for the SRV/DS/DNSKEY/TLSA/HTTPS/SVCB enum values that ALL apparently omits.

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 ('Look up DNS records of a name') and clarifies the ALL default and reverse-PTR behavior. It implicitly separates itself from siblings like lookup_mx and check_dmarc, but never names an alternative, so it stops short of full sibling differentiation.

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?

Explains what the default ALL does and that a single type can be requested, but gives no explicit when-to-use versus the sibling tools (lookup_mx, check_spf, check_dmarc) that overlap in domain-record territory. Usage is implied rather than directed.

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