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

Annotations already establish readOnly, idempotent, non-destructive and open-world behavior, but the description adds genuinely useful context the annotations cannot convey: that it is free, requires no wallet or payment, and takes no arguments. This is a real value-add beyond the structured safety hints.

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 [FREE] tag, that carries the cost, the payment prerequisite, and the parameter expectation without any waste.

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?

With no output schema and no parameters, the description's job is largely to explain that the return value is a sample. It does that ('see the shape'), though it gives no hint about the fields or volume of that sample, leaving a small gap for an agent deciding whether the preview is representative enough.

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 tool takes zero parameters, so per the rubric the baseline is 4. The description reinforces this with 'no arguments needed', which is consistent with the empty schema.

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 states this is a free sample response for social_trends_pulse, letting the caller see the output shape before paying. That is a specific verb+resource for a preview tool, though the underlying subject matter (social/trending topics) is only carried by the title rather than the description text itself.

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 clearly frames when to use it: before paying 0.015 USDC for the paid sibling, and it confirms no arguments are needed. It stops short of an explicit 'use this instead of social_trends_pulse when you only need the shape' instruction, but the routing intent is unambiguous.

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