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

Annotations already cover the safety profile (readOnly, openWorld, non-destructive), yet the description adds substantial context they cannot: the per-call price, the x402 payment path (USDC on Base/Solana/Polygon/Arbitrum), and a free sample input. Payment/auth mechanics are exactly the kind of non-destructive behavioral detail that adds value; only edge behavior on payment failure or rate limits is unstated.

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?

Front-loads what the tool does and the supported types before the usage, pricing, and sample sections. Dense and mostly waste-free, though the payment and free-sample sentences make it longer than a purely functional definition would need to be.

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?

There is no output schema, and the description compensates by stating the return shape ('records object with array per type'). Combined with the default behavior and supported types, an agent has everything needed to call and interpret this tool.

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 'domain' and 'types' are already fully documented, including the ["A"] default and supported enum values. The description largely restates these; the only marginal addition is the example object, which is illustrative rather than semantic. Baseline 3 applies when the schema does the heavy lifting.

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 ('Resolve DNS records for any domain') and enumerates the supported record types. This clearly separates it from neighbors like whois, domain_check, and ssl_check without needing to open a 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 concrete when-to-use scenarios mapped to record types: MX for mail setup, TXT for ownership, general use for propagation debugging. It stops short of naming an alternative sibling tool or stating when NOT to use it, so it does not reach a 5.

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