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

With no annotations, the description carries the full burden. It usefully discloses the resolver source, that results are live, and the paid access model ('x402 price $0.002/call (USDC, eip155:8453)'), which is real behavioral context. However it says nothing about failure behavior for nonexistent domains, caching/TTL freshness, rate limits, or timeouts.

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-loaded with the core verb and resource, followed by use cases and pricing in a compact two-clause form. The trailing price fragment is terse but not wasteful; nothing is padded.

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 lookup with no output schema and no annotations, the description covers purpose, context and cost but is silent on what a response looks like (record values, multiple answers, error shape for NXDOMAIN). An agent can call it correctly but cannot anticipate the result.

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 description coverage is 100% and both parameters are documented with the record-type enum, so the schema does the heavy lifting. The description's record-type list mirrors the enum and adds no syntax or format detail (e.g. whether domain accepts subdomains, IDN, or trailing dots).

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 ('Query live DNS records') and enumerates the record types supported (A, AAAA, MX, TXT, NS, CNAME, SOA), which the agent can map directly onto the schema enum. It also names the resolving backend (Cloudflare DNS-over-HTTPS), distinguishing it from lookups like live_ip_lookup.

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 use cases ('domain validation, email deliverability pre-checks and infrastructure discovery'), which tells the agent when this tool is the right pick. It does not name alternatives (e.g. live_ip_lookup) or state when not to use it, so it stops short of full routing guidance.

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