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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely useful context — the $0.005 USDC per call cost and x402/credits payment path — but says nothing about rate limits, failure modes, or resolution behavior beyond annotations.

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 short sentences, front-loaded with the core capability and followed by the cost. Zero filler; every clause 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 simple read-only lookup with no output schema, the description plus annotations plus schema cover what an agent needs to invoke it. Cost is disclosed, though record-type defaults and return shape are left entirely to the schema.

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 the baseline is 3. However, with no enums declared, the description's enumeration of valid record types (A, AAAA, CNAME, MX, NS, TXT, SOA, CAA, PTR, SRV) adds real value beyond the schema's terse 'Record type, default A'.

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?

Specific verb ('Resolve') + resource ('DNS records') with an enumerated set of supported record types. This clearly distinguishes it from siblings like lookup_ip, lookup_whois, and lookup_domain_report.

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?

No guidance on when to use this tool versus lookup_domain_report, lookup_ip, or lookup_whois. The only contextual statement is about pricing, which does not help an agent select between siblings.

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