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

Annotations declare idempotentHint=true and destructiveHint=false, and the description adds valuable behavioral detail: authentication requirements, the specific key format, and the complete structure of failure responses including retry guidance. This exceeds what the annotations provide.

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 sentences that are front-loaded with the primary action, then prerequisites, then error behavior. No filler; every sentence adds distinct value.

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?

An output schema exists, so return values need not be explained. The description covers prerequisites and error shape. It could note the idempotent nature explicitly, but the annotations already cover safety.

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 the schema already documents both parameters. The description mentions the API key and its format, but adds no syntax or format details beyond what the schema provides for product_id or the key. Baseline 3 is appropriate.

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+resource ('Add a catalog product to your account watchlist') and explains the consequence ('the price scheduler keeps updating it'). It distinguishes itself from siblings like track_product and unwatch_product by being the watchlist-add action.

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?

Explains the intended effect and prerequisite (API key) clearly, implying when to use it (to start watching a product). It does not explicitly contrast with sibling tools like track_product or unwatch_product, which would strengthen routing, but the context is clear.

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