check_domain_mx

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

With no annotations provided, the description carries the full behavioral burden. It reveals that the tool performs a read-only DNS/MX inspection via GET, and precisely explains the returned fields and their meaning. It does not cover error cases or permissions, but for a simple preflight check the disclosure is solid.

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 concise sentences front-load the purpose and immediately deliver the endpoint and return shape. Every sentence earns its place: the first states the action and timing, the second specifies the response contract.

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 single-parameter read-only check with no output schema, the description is complete: it states what it checks, when to use it, and exactly what the response contains. No critical missing context would prevent an agent from selecting or invoking the tool correctly.

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?

The input schema already provides 100% coverage by describing 'name' as the hostname to check with an example. The description reinforces that the hostname is the subject of the MX preflight but adds no significant format or constraints beyond the schema, so the baseline score of 3 applies.

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?

The description names a specific verb and resource: checking MX records for a hostname as a preflight step before enabling receiving. It also includes the HTTP endpoint (GET /domains/mx-check), which makes the tool's function unmistakable and distinct from the many domain and email siblings.

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?

The description clearly states when to use the tool: as an MX preflight check before enabling receiving. It does not explicitly name alternatives or exclusion conditions, but the usage context is specific enough that an agent can determine applicability without further inference.

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