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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The word "published" adds genuine behavioral context — unpublished or draft vendors are not returned — but the description says nothing about not-found behavior or what a miss looks like.

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?

A single eight-word sentence with no filler, and the distinguishing constraint ("published") plus the lookup key are front-loaded. Nothing could be removed without losing signal.

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 one-parameter read tool with full annotation coverage, the definition is nearly sufficient. The one real gap is that no output schema exists and the description gives no hint of what a returned vendor contains, though this is minor at this complexity.

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?

There is a single parameter with 100% schema description coverage, including pattern and length constraints, so the schema does the heavy lifting; baseline is 3. The description's "by its slug" only restates the schema's lookup key without adding format or resolution detail.

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 (get), resource (one published vendor), and lookup key (slug), so an agent can tell it apart from search_listings and the list_* siblings. It stops short of explicitly naming those alternatives, which keeps it out of 5 territory.

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?

"By its slug" implies the precondition that the caller already has a known slug rather than search criteria, which is useful implied routing away from search_listings. However, no when-to-use or when-not-to-use guidance is stated explicitly, and no alternative is named.

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