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 description adds value beyond them by enumerating the returned payload (URL, category, style, stack, palette, fonts, sections, screenshot link, similar-site links), which matters because there is no output schema. It omits failure behavior for an unknown slug, so not a 5.

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 front-loaded sentence that identifies the operation and lookup key before the payload list. The field enumeration is long but earns its place as a substitute for a missing output schema; only slight tightening is possible.

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 one required param, rich annotations and no output schema, the description covers the operation, the key's provenance and the return shape, which is what an agent needs. The only gap is the not-found/error case, which the agent must infer.

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% and the schema already gives a format example ('linear'), so the baseline is 3. The description adds origin semantics by tying the slug to search_sites results, which is meaning the schema does not convey.

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 and resource ('Get one SaaS website from the catalog by slug') with the key lookup key stated up front, plus an enumeration of what the record contains. It is clearly distinguishable from search_sites, which is named as the source of the slug.

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 parenthetical '(from search_sites)' tells the agent this is a follow-up call to a search result, which is a clear usage context. It does not state exclusions (e.g. batching multiple slugs, or when to prefer list_site_links for relationship data), so it stops short of full when/when-not guidance.

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