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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds one real behavioral detail — only published listings are returned, so unpublished slugs presumably yield nothing/error — but says nothing about not-found behavior or return shape.

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?

One short sentence, front-loaded with the verb and resource, with no filler. It is perhaps too terse — the "published" constraint could be foregrounded as a caveat rather than buried as an adjective.

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 simple single-param read tool with full annotations, the description covers the core contract: one published entity looked up by slug. With no output schema, the absence of any indication of what a successful response contains or what a miss looks like is a minor but real gap.

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?

Single parameter with 100% schema coverage including pattern and length constraints, so the schema fully documents it. The description only restates "by its slug" and adds no format or lookup semantics beyond the schema; baseline 3 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?

Specific verb+resource with scope qualifiers: "one" single item, "published", and "by its slug" — clearly a point lookup rather than the list/search siblings. It doesn't explicitly name search_listings or the list_* tools, so differentiation is implied by "one" rather than stated.

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 prerequisite of an already-known slug, which mildly steers an agent away from this tool when it only has a name. There is no explicit when-to-use/when-not or pointer to search_listings for slug discovery.

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