guess_email

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

With no annotations, the description must carry the full burden of behavioral disclosure. However, it only states the core function and does not reveal that the tool is probabilistic, may return multiple guesses, or how it handles failures. It also omits any mention of the optional 'fromEmail' parameter's role in SMTP verification, which could indicate a side-effect or external interaction.

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, front-loaded sentence that immediately communicates the tool's purpose. It contains no filler words and every element contributes to understanding. It is appropriately concise for a tool of this apparent simplicity.

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 an output schema and annotations, the description must convey expected return values and behavioral nuances. It does not mention whether the tool returns one email, multiple candidates, a confidence score, or how to handle invalid domains. It also fails to position the tool within the broader email workflow (e.g., pairing with 'verify_email'). This leaves significant gaps for an agent trying to use the tool effectively.

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 provides 100% coverage of parameter descriptions, so the baseline is 3 as per the rubric. The description adds no extra parameter-specific meaning beyond restating that the guess is based on 'name and domain.' It does not clarify usage of 'fromEmail' or any optional behavior beyond what the schema already states.

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 function: 'Guess an email address based on name and domain using common email patterns.' It uses a specific verb ('guess'), identifies the resource ('email address'), and specifies the input basis (name and domain). This distinguishes it from sibling tools like 'verify_email' or 'check_domain_catch_all', which serve different purposes in the email workflow.

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 provides no guidance on when to use this tool versus alternatives. It does not mention using 'verify_email' to check the guess, nor does it indicate any prerequisites or exclusions. The usage is entirely implied by the name and function, but the rubric expects explicit or at least contextually clear guidance, which is absent here.

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