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

Annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=false, so the agent knows it's a safe, read-only call. The description adds that it retrieves a 'live' listing, implying the listing must be live, and it specifies the exact fields returned and the slug format, which provides useful behavioral context beyond the annotations. The description does not contradict annotations.

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?

The description is a single sentence, concise and front-loaded with 'One live SaaSCity listing by slug', immediately stating the purpose and parameter. It lists the return fields efficiently without excessive detail. It's slightly dense but earns its length.

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 read-only, single-parameter tool with a rich output schema and annotations covering safety, the description is complete: it specifies the input (slug), the output fields, and the nature of the data ('live'). It doesn't mention pagination or error cases, but those are less critical given the tool's simplicity and the annotations.

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 coverage is 100%, as the schema fully describes the 'slug' parameter, including its meaning and format. The description also mentions the slug is the last part of the URL, which adds a little context, but since the schema already covers it, the description adds minimal extra semantics.

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 clearly states the tool fetches a single SaaSCity listing by slug, and enumerates the fields returned. It distinguishes from siblings by specifying 'One live listing' and 'by slug', though it doesn't explicitly contrast with search_listings or get_leaderboard, so it's clear but not fully differentiated.

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?

The description implies usage when you need a specific listing's details by slug, but it doesn't explicitly state when to use this versus search_listings (e.g., for filtering or searching) or get_leaderboard. It says 'One live ... by slug', which implies direct access, but no explicit guidance on alternatives or when not to use it.

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