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

With no annotations provided, the description carries the full burden. It states 'No authentication required', indicating a public endpoint and a safe read operation. It does not disclose data freshness, rate limits, or response format, but for a simple list retrieval, this may suffice.

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 only two sentences, concise and front-loaded. Every sentence adds value: the first states the core action, the second provides usage context and authentication requirement.

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 simplicity of the tool (no parameters, no output schema needed), the description covers the key aspects: what is retrieved, why it's used, and authentication status. It could mention the return format, but the use case is clear enough.

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 tool has no parameters, so the schema coverage is 100%. The description does not need to add parameter semantics, but the baseline is 4 for zero-parameter tools. No further detail is required.

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 retrieves 'currently approved DKIM vendor domains' from a specific endpoint, using specific verb 'Get' and resource 'vendor domains'. It is distinct from sibling tools.

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 explains that standalone agents use this list to seed Gmail searches and that unknown vendors are queued, providing context for when to use it. It also notes that no authentication is required. However, it does not explicitly state when not to use it or mention alternatives.

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