Verify Email

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

Annotations already indicate readOnlyHint and openWorldHint. The description adds concrete behavioral details: cost of 1 credit per call, charged even if the email is not found, and the specific return levels (ultra_sure, sure, risky, invalid, not_found). This significantly enhances transparency beyond 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 mostly focused, but includes a redundant title line. Every sentence adds information (purpose, cost, return values), though the structure could be slightly tighter.

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?

For a simple verification tool with no output schema, the description adequately covers return values, cost, and behavior. However, it lacks usage context and does not explain the meaning of the return levels, leaving some gaps for the agent.

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 coverage is 100% with a single required 'email' parameter. The description's 'Choose email column' adds no extra semantics or format guidance beyond the schema. Baseline 3 is appropriate for high 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's purpose: 'Check if an email address is valid' and lists the return certainty levels. It uses a specific verb 'verify' on a specific resource 'email', and while sibling tools exist (e.g., derrick_find_email), the action of verification is distinct.

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 on when to use this tool versus alternatives. The description mentions cost and charging even for not_found, which is a soft usage hint but does not compare to sibling tools or provide context for selection.

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