validate_email

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

With no annotations, the description carries the full burden, and it does disclose the three validation layers, which is useful behavior. However, it says nothing about whether network/DNS lookups make it slow or costly, whether results are cached, or whether it has side effects, and there is no output schema describing the result shape.

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?

A single sentence, front-loaded with the action and resource, with zero padding. Every clause (syntax, DNS, deliverability) earns its place.

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?

There is no output schema, so the description ought to explain what a validation result looks like (boolean, score, reason codes), and it does not. For a one-parameter read-style check it is otherwise adequate, but the return semantics are a real gap.

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% for the single 'email' parameter, so the schema already documents it. The description adds no format or syntax guidance beyond that, so the baseline of 3 applies.

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 names a specific verb ('Check') and resource ('an address') and enumerates the three checks performed (syntax, DNS, deliverability), so an agent knows exactly what it does. It does not explicitly distinguish itself from nearby siblings like verify_domain, though the resource difference is self-evident.

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?

Usage is only implied: the deliverability check suggests running it before send_email, but there is no explicit 'use this when...' guidance, no exclusions, and no mention of alternatives or prerequisites.

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