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

With no annotations, the description carries the full burden. It mentions 'Billing per call: 1 Credits', which discloses a cost, and 'instantly' suggests speed. However, it does not describe what verification does (e.g., checks syntax, domain existence), side effects, or outcome behavior. This is insufficient transparency for a tool with no structured annotations.

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 short and front-loaded, which is good for conciseness. However, the billing info is awkwardly appended and the content is too sparse to be functional. It is appropriately brief but lacks essential detail, so a middle score is warranted.

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 tool's simplicity (one parameter, no complex schema), the description should at least explain what verification means and any limitations. It only repeats the title and adds a billing note, providing no meaningful context. This is inadequate even for a simple tool, especially with no annotations or output schema to rely on.

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 0%, so the description must compensate. The only parameter is 'email', which is self-explanatory due to its name, but the description adds no additional meaning, format constraints, or usage notes. The schema itself has an example but no description. Thus, the parameter semantics are under-explained.

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 verb 'Verify' and the resource 'email', which conveys the core purpose. It distinguishes from the name 'get_email' by indicating the action is verification, not retrieval. However, it lacks specifics on what 'verify' entails (format, deliverability, etc.), 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 provided on when to use this tool versus alternatives, nor any exclusions or prerequisites. The fact that it verifies an email implies usage for that purpose, but there's no explicit context, and no sibling tools exist. This is minimal guidance, so it earns a 2.

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