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

No annotations exist, so the description carries the full behavioral burden. It adds useful context: the default limit and the payment model (5 free trial calls per signed wallet). However, it does not state that the operation is a pure read with no side effects, nor anything about pagination or return size.

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?

Single front-loaded sentence stating the resource, scope, and default, followed by a short pricing tag. No wasted prose, though the emoji/pricing fragment is slightly noisy.

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 two undocumented string parameters, no output schema, and no annotations, the description leaves 'n' undefined and gives no sense of return shape. For a tool whose inputs are opaque strings, more explanation is required.

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 description coverage is 0% for 2 parameters. The description hints at what 'limit' does via the default of 1000, but the parameter 'n' is entirely unexplained in both schema and description, leaving an agent unable to know its purpose or format.

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 verb and resource ('Lists perfect numbers') with the scope ('up to a limit'), which distinguishes it from siblings like x402-is-perfect-number and x402-abundant-numbers. It is clear what the tool returns, though it never explicitly contrasts itself with those neighbors.

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 default limit of 1000 is disclosed, but there is no guidance on when to use this listing tool versus the many sibling primality/number-check tools (x402-is-perfect, x402-abundant-numbers). No prerequisites or exclusions are given.

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