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

Annotations already declare non-read-only, non-idempotent, non-destructive, closed-world behavior. The description adds genuinely new context: the target is the signed-in user's stack (implying auth scope), the operation has no purchasing side effect, and the id originates from a search/product result. It does not warn about duplicate entries despite idempotentHint=false, which is the one remaining gap.

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?

Four tight clauses front-loaded with the usage trigger, then the action, then parameter sourcing, then the boundary against the cart tool. No sentence is redundant.

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 single-parameter, no-output-schema write tool this is nearly complete: intent, auth scope, parameter sourcing, and the cart boundary are all covered. Only duplicate/idempotency behavior and the resulting state change are left unstated.

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% but the schema text is terse ('SuppCo Product ID'). The description adds real value by specifying the accepted formats (UUID or slug) and where to source the value (a search or product result), which the schema does not say.

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 ('Adds the product to the ... user's stack') and immediately separates itself from the nearest sibling by clarifying it is tracking, not purchasing. An agent can distinguish it from suppco_add_to_cart, suppco_remove_from_stack, and suppco_manage_stack 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 an explicit when-to-use trigger ('when the user wants to start tracking a product') and an explicit when-not with a named alternative ('this does not buy anything; to buy a Buying Club product, use suppco_add_to_cart'). The routing decision is fully resolved in the text.

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