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

Annotations already declare readOnly, idempotent and non-destructive, so safety is covered. The description adds genuinely new behavior: an unknown id returns not-found rather than guessing, and the record carries more fields than a search hit (builder accounts, website, city, opt-in MRR, all-time clicks/impressions). It stops short of describing auth, rate limits, or pagination, 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?

Purpose and the returned-field summary are front-loaded, then usage guidance, then the id-format caveat and error behavior. It is somewhat long at six sentences with mild redundancy between "anything specific about a single product" and the field enumeration, but every sentence carries actionable information.

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?

There is no output schema, so the description carries the return-value burden and does so by enumerating the notable fields (attribution, links, funding state, engagement stats). Combined with the not-found behavior and id-format rule, an agent has everything needed to call 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?

Schema coverage is 100% and the single parameter is already documented with an example, so the baseline is 3. The description goes further by clarifying that ids are the slug in the product URL, not the display name, and that the id is the only accepted input, adding real disambiguation value.

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 and resource ("Retrieve one product by its directory id") and immediately scopes it against the sibling search_products by declaring it returns strictly more per record than a search result. An agent can distinguish this from search_products and fetch without opening a schema.

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?

Gives explicit when-to-use ("anything specific about a single product", filling out a shortlist after a search) and explicit when-not-to-use ("Do not call it to discover products... it cannot answer 'find me X'. Search first."). The alternative tool is named and the condition that selects it is spelled out.

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