check_email

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

With no annotations provided, the description carries the full burden of disclosing behavioral traits but fails entirely. It does not indicate whether this is a read-only validation, a network call to external services, potential rate limits, or what the return value indicates (boolean, string error message, object?).

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 extremely brief (4 words), which prevents verbosity, but it is under-specified rather than efficiently concise. It is front-loaded but fails to earn its place by providing actionable information about the tool's behavior.

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 lack of output schema and annotations, the description should explain the check methodology and return behavior. For a single-parameter tool, it provides the bare minimum identification but leaves critical gaps in explaining what the tool actually returns or accomplishes.

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 100% (the parameter includes an example value). The description mentions 'email address' but adds no semantic value beyond the schema—no format requirements, validation rules, or domain constraints beyond what's implied by the parameter name and example.

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 'Checks given email address' is essentially a tautology of the tool name 'check_email'. It fails to specify what 'checking' entails—whether it validates syntax, verifies existence via SMTP, checks MX records, or something else.

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 provided on when to use this tool versus alternatives, prerequisites (like API keys for verification services), or when not to use it. The description is purely declarative with no contextual usage hints.

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