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

Annotations already declare readOnlyHint, idempotentHint, etc., so safety is covered. The description adds that no payment or authentication is needed, which is valuable context beyond the annotations. It doesn't describe the return format, but as a preview that's less critical.

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?

Two concise sentences, front-loaded with [FREE] and the key differentiator. Every word 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?

Given zero params and rich annotations, the description adequately covers the tool's purpose and usage. It could briefly mention what the signal represents, but for a free preview the current level of detail is sufficient.

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?

Zero parameters, so baseline is 4. The description confirms no arguments are needed, which aligns perfectly 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 it's a sample response for signal_day, showing the shape before paying. It clearly identifies the premium counterpart, though the actual content of the daily signal isn't described beyond being a sample.

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?

Explicitly says 'No wallet, no payment, no arguments needed,' clearly indicating when to use this free preview versus the paid signal_day. The sibling context makes the preview/paid pattern evident.

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