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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive. The description adds the behavioral detail that this tool 'runs a fresh scan', indicating it performs an active operation rather than just reading cached data. This goes beyond the annotation safety profile without contradicting it.

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, concise sentence that front-loads the primary purpose and includes the key nuance of running a fresh scan. Every word adds value; there is no redundancy or filler.

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?

With one simple parameter and no output schema, the description adequately conveys what the tool returns ('overall deliverability score and letter grade'). It could mention the output format or scan timing implications, but for this simplicity level it is largely complete.

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 description for 'domain' ('Domain to score, e.g. example.com') already provides clear semantics. The tool description does not add any additional parameter-level meaning, so a baseline score of 3 is appropriate given 100% schema coverage.

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 states the tool returns an 'overall deliverability score and letter grade' for a domain, with the specific verb 'Return'. It also notes 'runs a fresh scan', distinguishing it from potentially cached report tools like 'get_deliverability_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 phrase 'runs a fresh scan' implies this tool is for getting up-to-date data, but it does not explicitly state when to use this over siblings like 'get_deliverability_report' or 'scan_domain'. Usage context is only implied, not fully articulated.

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