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

Annotations already cover the read-only/idempotent/non-destructive profile, so the bar is lower; the description adds the monetization boundary ('free, no payment', what stays paid) and the aggregate-only data scope. It does not discuss rate limits or caching, but the added billing/data-boundary context is meaningful.

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 free/no-payment value proposition and the aggregate scope, then the paid boundary. Two sentences, dense but each clause carries routing information; the trailing endpoint list is somewhat heavy but serves as explicit alternative routing.

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?

An output schema exists, so return values need not be re-explained; the description still names the headline fields and clearly delineates what this free call does not return. Complete for a zero-parameter liveness 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 sets the baseline at 4. The description's enumeration of returned metrics is output rather than parameter semantics, so nothing further is needed or expected here.

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?

States a specific function (liveness proof of the x402 rail-intelligence routes) and precise scope (only headline totals of the 30-day demand map, aggregates only). It is clearly distinguishable from the paid x402 siblings it names.

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?

Explicitly frames this as the free/no-payment entry point and names the paid alternatives (GET /market/x402-overview, /market/x402-top-sellers, /market/x402-host-demand, /market/x402-payer-bands, /market/token-verdict) with the condition that selects them – per-host detail and risk verdicts.

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