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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds the critical behaviors annotations cannot: it is a paid tool (0.10 USDC on Base via x402), the two-step challenge/sign flow, that the calling agent's own wallet pays, and that the server never holds or uses a wallet. That is exactly the kind of auth and cost context an agent needs.

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?

Front-loaded with the [PAID] tag and price, then the resource, then the payment procedure. Four sentences that mostly earn their place, though the price is stated twice ('0.1 USDC' and '$0.10 USDC on Base'), which is minor redundancy.

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 a paid, two-step interaction, the description covers the payment lifecycle, wallet ownership, and day-range semantics completely. The main omission is any hint of what a 'brief' contains, but for a paid archive fetch the invocation-critical information is present.

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?

Schema coverage is 100%, so the baseline is 3. The description adds genuine meaning beyond the schema: cost is flat regardless of day count (so days is not a pricing lever) and payment_header is optional on the first call, defining the same-arguments-replay contract. This enriches the parameter behavior rather than repeating schema text.

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: returns the last N days (1-30) of Daily Agent Signal briefs from a proprietary archive. An agent can infer this is the multi-day counterpart to signal_day/signal_latest, though no sibling is named explicitly. Purpose is clear but not differentiated by name.

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 operational guidance for the paid flow ('Call with no payment_header first to receive the payment requirements') and signals the multi-day use case via the 1-30 day range and flat pricing. It stops short of naming signal_day/signal_latest as the single-day alternatives, so routing is inferred rather than stated.

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