Look up MX records for a domain

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

With no annotations, the description must carry the behavioral burden. It usefully discloses that the result is a list sorted by priority, but omits how failures are reported (e.g., NXDOMAIN, no MX records), timeouts, caching, or read-only semantics, so it is only partially transparent.

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, purpose front-loaded, return behavior immediately after. No filler, no redundancy, appropriately sized for a simple one-parameter DNS tool.

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?

Given the simple schema and absent output schema, the description should explain return values more fully (e.g., host/preference fields) and at least sketch error behavior. It covers the high-level return concept but leaves those gaps for an agent to guess.

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% and the sole parameter is fully documented in the schema, so the baseline is 3. The description adds no additional semantics about the domain parameter beyond what the schema already states.

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+resource: DNS MX-record lookup, and adds the return shape (sorted mail-exchanger list). However, it does not differentiate from sibling tools like check_email or is_disposable, which is why it falls short of 5.

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?

Usage is only implied: 'Standalone' suggests it needs no other context, and the purpose implies you call it when you need MX records. There is no explicit when-to-use statement, no exclusions, and no routing against the sibling email-verification tools.

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