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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safe read-only nature is covered without needing restatement. The description adds a critical behavioral fact: each successful call costs $0.01 USDC, which an agent must know before invoking the tool. It also clarifies that the output is early signals rather than final ranking data, and it does not contradict the annotations.

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 two short sentences with no filler or redundant phrasing. The value proposition is front-loaded, and the pricing note is appended compactly. Every word contributes to the agent's understanding of what the tool does and what it costs.

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 read-only tool with one optional parameter and strong annotations, the description provides enough context for selection and invocation. It covers the core output concept, the early-signal positioning, and the cost per call, while the schema handles the limit parameter. It does not specify time window, ordering, or exact output shape, which keeps it just short of fully complete.

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 only parameter, limit, is fully documented in the input schema with its default, minimum, maximum, and meaning, giving 100% schema coverage. The description adds no parameter-specific details, but the schema already provides everything needed. This matches the baseline for a fully documented single parameter.

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 clearly indicates that the tool surfaces sudden inflow spikes and first-seen large payers, positioning these as early signals before they appear in rankings. It lacks an explicit verb like 'lists' or 'returns', so it is a noun-phrase description rather than a full purpose statement. It partially distinguishes from rankings but does not name sibling tools.

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?

The phrase 'before they show up in a ranking' implies a use case around early detection of movers, which provides some contextual guidance. However, there are no explicit when-to-use instructions, exclusions, or named alternatives among the sibling tools. An agent must infer when to choose this over x402_new_entrants or x402_trending_services.

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