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

Annotations already cover readOnly/idempotent/non-destructive, and the description adds genuinely new operational context: it is free, requires no wallet, no payment, and no arguments. That is real behavioral value beyond the structured fields.

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 front-loaded sentence leads with '[FREE]' and packs purpose, cost, and the no-argument fact without padding. Every clause 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?

For a zero-parameter preview tool with no output schema, the description tells the agent what it gets (a sample response showing the shape) and that no setup is needed. Adequate, though it could say more about what the sample contains.

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, which is the baseline-4 case, and the description reinforces this with 'no arguments needed.' Nothing further is required.

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 the concrete resource it mirrors ('company_lookup (Company identity lookup (SEC EDGAR + GLEIF LEI merge))') and states it returns a sample response, so an agent can distinguish it from the paid sibling. It is clear but relies on restating the title rather than adding new distinguishing detail.

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 an explicit condition for use: 'so you can see the shape before paying 0.01 USDC,' which routes the agent to this tool first and the paid company_lookup afterwards. It stops short of an explicit when-not statement, but the intent is unambiguous.

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