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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds context the annotations cannot: it is free, needs no wallet or payment, takes no arguments, and that editions are not published daily (check /health for the date). That is meaningful additional behavioral context.

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 '[FREE]' tag and the sample-response purpose are front-loaded, and each clause routes the agent somewhere useful. It is somewhat long and devotes most of its text to when to buy the paid sibling rather than the preview itself, but no sentence is wasted.

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 zero parameters, the description carries the burden of orienting the agent. It describes the artifact ('the ranked judgment on agent-economy demand') and the payment/routing context well, though it does not describe the preview's actual return shape or size, which would fully close the loop for a preview tool.

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. The description reinforces this ('No wallet, no payment, no arguments needed'), so nothing is missing and nothing needs compensating.

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 verb and resource ('A sample response for signal_latest ... see the shape before paying 0.03 USDC') and immediately frames its identity as the free preview variant, distinguishing it from the paid sibling and the other signal_* tools. An agent can tell what this returns 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-use ('Buy signal_latest when you want the most recent stored edition'), when-to-skip ('Skip it when you already hold an earlier brief'), and names the correct alternatives for each case (signal_delta, signal_day, signal_history). Nothing is left to inference.

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