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

Annotations already declare readOnly, idempotent, non-destructive, and openWorld, so the safety profile is covered. The description adds genuinely useful context beyond them: it is free, requires no wallet, no payment, and no arguments, which tells the agent it can be invoked safely and cheaply as a probe.

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 compact sentence with the '[FREE]' qualifier front-loaded so the cost implication lands first. The nested parenthetical restating the paid tool's title is slightly redundant and adds length without much value.

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-parameter preview tool with no output schema, the description covers what an agent needs: it is free, argumentless, and returns a sample of the paid tool's output shape. The only omission is that it does not describe the sample contents, which is acceptable since the tool's purpose is precisely to reveal them.

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 100%, so the baseline is 4. The description reinforces this with 'no arguments needed', which correctly sets the expectation that the tool takes no input.

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 returns a sample response for address_geocode so the agent can inspect the shape before paying, which is a specific and non-tautological purpose. It implicitly distinguishes itself from the paid sibling address_geocode via the '[FREE]' tag and the preview framing, though it never names the paid tool as the alternative explicitly.

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 condition for use: call it to see the response shape before spending 0.008 USDC. It does not spell out when NOT to use it (e.g. when real geocoding data is actually needed), but the preview-vs-paid context is easy to infer from the sibling name address_geocode.

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