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

With no annotations supplied, the description carries the burden and does meaningful work: it discloses that prices are live, that limits exist, that sponsored placement is labelled, and — importantly — that three-month reach figures are 'a projection, not a promise'. It says nothing about access requirements or whether pricing can change between call and purchase.

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?

Three sentences, front-loaded with what the catalog is, then its contents, then the call-order rule — the action guidance lands last where an agent will still see it. The middle sentence is long and carries several ideas at once, but each clause (slug, next free date, reach disclaimer) is load-bearing.

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?

This is a zero-parameter read tool with no output schema, so the description must convey the return shape — and it does, listing guide slugs, next free dates, reach projections, prices, and limits. Combined with the explicit call-order rule, an agent has everything needed 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?

The tool takes zero parameters and schema coverage is 100%, so there is no parameter meaning to add. The baseline for a parameterless tool applies.

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 names a concrete resource (the Hokai vendor catalog) and enumerates its three purchasable categories — listings, labelled guide spots, and buyer leads — plus the guide-level data bundled in. An agent can tell this is the discovery/pricing surface rather than one of the purchase actions.

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 gives explicit sequencing: 'Call this before buy_listing, buy_guide_spot or buy_leads', naming three siblings and the condition that selects this tool over them. It stops short of saying when *not* to call it or how it relates to read-side siblings like get_listing_info or order_status.

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