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

Annotations already declare read-only, idempotent and non-destructive, so the safety profile is covered. The description adds genuinely new behavior: the API-key prerequisite with a URL to obtain it, and a precise failure contract (error.code, retry_recommended, retry_after_seconds) which effectively signals rate limiting.

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?

Three short sentences, purpose front-loaded, then credential requirement, then error shape. No filler, though the error-field enumeration is slightly dense for a description that already has an output schema.

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 a rich annotation set and an output schema, the description need only cover prerequisites and failure semantics, which it does. Nothing essential is missing, though it stops short of saying what a positive result contains or whether unwatched products are reported as false vs. an error.

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%, so both parameters are already documented, and the description adds little for product_id. It does add the origin of the api_key credential (profile#api-keys), which is modest value beyond the schema's 'pwk_live_...' hint, matching the baseline 3.

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: 'Check whether your account watches a product' states exactly what is returned for a single product. It is distinguishable from list_watchlist (enumerate all) and watch_product/unwatch_product (mutate), though it never names those siblings explicitly.

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?

Usage is only implied: an agent can infer this is the single-product status lookup rather than a listing or a mutation. No explicit when-to-use, when-not, or routing to list_watchlist for a full enumeration is given.

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