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

Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds meaningful context beyond that: it costs nothing, requires no wallet, no payment, and no arguments, which is exactly the behavior an agent needs before calling. It stops short of describing the response structure in detail.

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 and the key constraints. Nothing is repeated or wasted; the cost, purpose, and auth requirements all appear immediately.

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 full annotation coverage and no output schema, the description is nearly complete: it explains what is returned (a sample response), the cost (free), and the auth requirements (none). The only minor gap is that it does not describe the sample payload's fields, but a preview inherently defers that to the actual response.

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 line 'no arguments needed' reinforces the empty schema rather than adding new semantics, which is appropriate for a no-arg tool.

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 a specific purpose: it returns a sample response of the edgar_filings tool so the caller can see the output shape before paying. It names the sibling resource it is a preview of (edgar_filings / SEC EDGAR filings), letting an agent distinguish it from the paid sibling without opening the schema.

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: run this to preview the shape before paying 0.02 USDC. The routing intent (free trial vs. the paid edgar_filings tool) is explicit, though it never states an explicit exclusion or contrast sentence naming the paid tool by name for the actual data.

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