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

No annotations exist, so the description carries the full burden and does so well: it states nothing is charged by the call, that a Stripe checkout_url is returned for a person or paying agent to complete, that payment creates the vendor account and triggers an email, that rankings are unaffected, and that refunds require contacting damien@hokai.io. These are exactly the side-effect and irreversibility facts an agent needs before invoking a purchase flow.

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-loads the action, then the return value, then the eligibility constraint, then Args — a sensible order with no filler. Slightly long, and sentences like 'A person then researches the product and writes its page' are context rather than call-critical, but they earn their place by setting expectations about the paid flow.

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 output schema and no annotations, the description still explains the return value (checkout_url), the human follow-up, the account creation side effect, and the refund path. Only edge cases like errors or what happens if checkout is abandoned are unaddressed, which is a minor gap for a 5-parameter purchase 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?

Schema description coverage is 0%, so the description must compensate, and the Args block does: tool_url is 'the product's own website' with an example, email is a vendor work email tied to account creation, and company/note/agent are given intent rather than just labels. The company, note and agent entries remain thin ('company name', 'anything the editors should know'), so it doesn't fully document all five.

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?

Opens with a specific verb and resource: 'Buy a Hokai listing' scoped to AI tools, models, agents, MCP servers, skills or services. It doesn't name a sibling such as submit_listing or buy_guide_spot to contrast with, but the 'one-time fee' and 'checkout_url' framing implicitly separates it from a free submission path.

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?

Contains an explicit eligibility gate: 'Only call this when the product's owner or their team asked for it,' plus a constraint to use their real work email. That is clear when-to-use guidance with a strong negative condition, though no sibling alternative is named for the case where the user is not the owner.

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