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

Annotations only say readOnlyHint=false and openWorldHint=false, so the description adds meaningful behavioral context: registering a standing interest, catching changes at the moment they happen, optional callback via POST, and the per-call price. It could go further by disclosing watch lifecycle or cancellation behavior, but the core side effects are clear.

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?

The description is compact and front-loaded: purpose, usage guidance, then cost. Every sentence earns its place and none are redundant with the 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?

Given six parameters, a fully descriptive schema, and no output schema, the description covers the essential context: purpose, when to use it, how the tool behaves, and cost. The main gaps are lifecycle details (whether/canceling a watch) and what the registration call returns, but these are not required to invoke 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 description coverage is 100%, so the schema already documents all six parameters and their requirements. The description's prose restates the high-level event types (price drop, back in stock, store reach change) but does not add parameter semantics beyond what the schema already provides.

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?

The description opens with a specific verb and resource: 'Register standing interest in a product or a store,' and enumerates the event types (price drop, back in stock, reach change). It also explicitly distinguishes itself from the sibling tool find by saying to call it instead of polling find on a schedule.

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?

The description has a dedicated 'When to use' section that names the alternative (find), states the condition for this tool ('instead of polling find on a schedule'), and gives a concrete reason (cost and immediacy). This is explicit selection guidance.

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