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

With no annotations, the description carries the full burden and does substantial work: it discloses that payment is required (US$3.00 USDC on Base via x402, or 3700 sats via Cashu/L402), that output is proof links, and that rate-limited leftovers are queued. This is meaningful behavioral context beyond the schema. It stops short of stating reversibility or full failure semantics.

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 key action and directory list are front-loaded, and the sentences are dense but purposeful. It is slightly cluttered with pricing and endpoint reference fragments, but nothing is egregiously wasted.

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 paid, side-effecting tool with no annotations and no output schema, the description covers the essentials: what is produced (proof links), the cost/payment rails, and rate-limit queuing behavior. Return format specifics and idempotency are left implicit, but the agent has enough to invoke it correctly.

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 100%, so the schema already documents both url and contact. The description restates the usage pattern (url=https://your.origin, optional contact=email) but adds no format or validation detail beyond what the schema provides. Baseline 3 is appropriate.

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 (List) and resource (your x402 agent/API origin) and names the concrete target directories (agent402.tools, 402index.io, x402dash). It also implicitly distinguishes itself from the list_me_info sibling by pointing at the free GET /list-me info endpoint, so an agent can tell the paid listing action apart from the free info lookup.

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 description conveys that this is a paid listing action on 'free no-account directories' and cites a cost, which implies when it applies. However it never explicitly says when to use this versus list_me_info or the other listing-related siblings; the routing to the free info endpoint is only implied via the URL reference, leaving the choice to inference.

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