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

Annotations already declare readOnlyHint=false, idempotentHint=true, openWorldHint=true, and destructiveHint=false. The description adds genuinely non-obvious behavior beyond that: the listing is free, is labelled 'unpaid', and is only actually published if live validation of the endpoint succeeds — a conditional-acceptance rule an agent could not derive from annotations or schema.

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 short sentences with the core action front-loaded and the eligibility caveat second. 'It is called unpaid' is slightly cryptic phrasing but carries real information about how the listing appears; there is little wasted text.

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 write operation with no output schema, the description omits what a successful call returns (a listing record? an id?), whether authentication or account ownership is required, and whether verification is synchronous or asynchronous. The key precondition is covered, but an agent cannot predict the result of the call.

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 url and method parameters are already documented in the schema. The description adds a partial constraint on the URL (must be on an OMNIGATE or 402Proof network) but leaves the term 'network' undefined and says nothing about the method parameter, so it does not meaningfully improve on the schema.

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 states a specific action on a specific resource — publishing your own x402 endpoint into the market — which distinguishes it from siblings like get_listing and search_catalog. The domain jargon ('x402', 'unpaid') is explained in passing but remains specialist, so an agent unfamiliar with the ecosystem needs to infer a fair amount.

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?

It implies usage through 'your own x402 endpoint' and gives an eligibility precondition (the endpoint must return a valid x402 v2 challenge on an OMNIGATE or 402Proof network). However, it never says when to choose this over a purchase-oriented sibling, nor what to do when the precondition fails.

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