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

Since no annotations were provided, the description carries the burden of behavioral disclosure. It provides valuable technical context by specifying that the checks are performed using 'DNS over HTTPS,' which is a significant detail about the operational behavior of the tool.

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?

The description is a single, dense sentence that front-loads the primary function and immediately includes technical specifications. Every word contributes to defining the tool's scope.

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?

Despite having no output schema, the description is highly complete regarding the tool's function and methodology. It provides the agent with all the necessary information to understand the operation and decide if it's the correct tool for a deliverability task.

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%, setting a baseline of 3. The description itself provides minimal semantic value, only restating that the input is a 'domain or email address' which is already defined in the schema.

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 clearly and specifically states the function ('deliverability check') and the resource ('domain or email address'). Crucially, it names the specific methods used (MX records, SPF, DMARC), which highly distinguishes it from sibling tools like `domain_age` or `domain_trust_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?

The description is silent on when to use this tool versus alternatives. While the specific checks listed (MX, SPF, DMARC) imply its use case, it doesn't explicitly guide the agent in choosing it over other domain-related reporting siblings.

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