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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds useful preview-specific context: it is free, requires no wallet or payment, takes no arguments, and exists to show response shape before purchase. It does not state sample limitations or freshness, so it falls short of a 5.

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?

The description is front-loaded with [FREE] and the core purpose, then immediately covers buy/skip conditions and alternatives. Every sentence earns its place, and there is no filler.

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-argument preview tool with rich annotations and no output schema, the description provides everything an agent needs: what it is, when to use it, when to avoid it, alternatives, cost, and argument expectations. No material gap remains.

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?

With zero parameters, the baseline is 4. The description reinforces that no arguments are needed, which matches the empty schema and removes ambiguity for an agent considering the call.

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 exactly what the tool returns: a free sample response for signal_continuity, a cross-day continuity map. It distinguishes the preview from the paid sibling and from other signal tools, so an agent can tell what it is 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 explicit when-to-buy guidance for the full tool versus when to skip the preview, and names concrete alternatives (signal_history, signal_topic_trace). This is unusually strong routing for a preview endpoint.

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