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

Annotations already declare mutation (readOnlyHint=false), idempotency, and non-destructiveness, so the bar is lower; the description nonetheless adds the recurring side effect (scheduler updates), the auth prerequisite with key prefix and URL, and the failure-path error shape including retry_recommended and retry_after_seconds. Nothing contradicts the 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?

Three front-loaded sentences: purpose, prerequisite, then failure behavior. No filler, though the enumerated error fields are somewhat verbose given a dedicated output schema already exists.

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 two-parameter mutation with full annotation coverage and an output schema, the description covers purpose, auth, and the failure contract adequately. The main missing piece is disambiguation from the sibling track_product, which matters for correct tool selection.

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 description coverage is 100%, with both api_key and product_id documented including prefixes, so the schema carries parameter meaning. The description only restates the key prefix and adds the profile URL for obtaining it, which is marginal added 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 ('Add a catalog product to your account watchlist') and even explains the downstream effect (the price scheduler keeps updating it). However, it never distinguishes itself from the near-duplicate sibling track_product, so an agent cannot confidently choose between them.

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 by the purpose statement; there is no explicit when-to-use, no exclusions, and no mention of the obvious alternatives track_product, unwatch_product, or get_watch_status. Given a sibling named track_product that appears to do the same thing, this omission is a real routing gap.

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