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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive, so the safety profile is covered. The description adds material context beyond the structured fields: it is free, requires no wallet or payment, and takes no arguments. It does not describe pagination, rate limits, or exactly what the sample contains.

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 efficient sentence front-loads the [FREE] tag and preview nature, then states the payment/argument facts. Every clause earns its place and nothing is repeated.

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 zero-arg, annotation-covered preview with no output schema, the description is nearly complete: it establishes cost, prerequisites (none), and purpose. It could say more about what the returned sample payload contains, but 'see the shape' adequately sets expectations for a preview tool.

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?

There are zero parameters and schema coverage is complete, so the baseline is 4. The description reinforces this with 'no arguments needed,' adding no contradictory or missing parameter meaning.

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 this is a free sample/preview response for domain_intel, and the title/description identify the underlying resource (domain identity & trust posture via RDAP + DNS email-auth). It distinguishes itself from the paid sibling domain_intel by being a no-cost shape preview. It stops short of describing what the preview content actually contains, but the preview-vs-paid distinction is unambiguous.

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?

It gives a clear reason to call it ('so you can see the shape before paying 0.012 USDC') and explicitly notes 'no wallet, no payment, no arguments needed.' The implied when-to-use (evaluate before paying for domain_intel) is present, though it never names domain_intel as the alternative tool explicitly or states when-not to use it.

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