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

With no annotations provided, the description carries the full burden of behavioral disclosure. It only mentions 'basic RFC 5322 format validation' without detailing outcomes, edge cases, or any side effects. There is no mention of what happens with invalid input or whether it performs additional checks beyond format.

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 core purpose. There is no wasted wording, though it is so brief that it borders on under-specification. Still, it is efficient.

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?

The tool is simple with one parameter and no annotations, but the description is too sparse to be complete. It explains the function but not the input semantics or usage context. Given the presence of an output schema, return format is covered, but the missing parameter explanation and usage guidance leave gaps.

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 has one parameter 'q' with no description and a default value. The description does not mention 'q' at all, so the agent has no idea what to pass. Since schema coverage is 0%, the description must compensate, and it fails to do so.

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 states a clear verb ('validates') and resource ('email format') and specifies the RFC 5322 standard, which distinguishes it from other email tools like 'email' or 'emailrep' that likely do more than format checks. However, it doesn't explicitly name siblings or contrast itself, so it's not a perfect 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?

No guidance is given on when to use this tool versus alternative email tools (e.g., 'email', 'emailrep', 'emailsec'). The description only states what it does, leaving the agent to infer context from the name and sibling list.

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