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

Annotations only declare readOnlyHint, so the description carries the rest and does well: it discloses that results are aggregate-only, come with uncertainty intervals and caveats, and — critically — that access is paid via x402 at 0.005 + 23% VAT = 0.00615 EURC or USDC on Base. That payment/precondition detail is exactly the behavioral context annotations cannot convey; only the volume of data returned is left unspecified.

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 tight sentences, with the returned content front-loaded and the payment terms second. The price arithmetic is slightly verbose but is genuinely actionable, so nothing here is waste.

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 parameters and no output schema, the description must carry the return shape and access cost, and it does both: metrics, uncertainty, sample sizes, two vantages, caveats, aggregates-only, and the exact payment rail and amount. An agent can decide and invoke correctly from this alone.

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 no parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. The description wisely does not pad with irrelevant input discussion.

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?

Names a specific resource (agent-infrastructure niches) and precisely what it returns: selection ratios of demand share over supply share, with 95% intervals, sample sizes, two vantages and caveats. An agent knows the payload shape, though the title 'Star map, full' adds nothing and there is no explicit verb distinguishing this from niches_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?

No when-to-use or when-not-to-use guidance, and no alternative is named even though niches_sample is a plausible sibling for a lighter fetch. The only usage constraint offered is 'Aggregates only', which hints at scope but does not route the agent between tools.

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