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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), so the description's job is to add substance, and it does: it discloses the exact signals compared (current lowest in-stock price, 90-day low, all-time low, high, watch duration) and the return shape (verdict + confidence). The explicit 'summary only, not full price history' boundary is valuable behavioral context beyond 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?

Two sentences, both load-bearing: the first defines the computation and output, the second defines the scope boundary. Nothing is repeated from the title or annotations, and the core operation is front-loaded.

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 no output schema, the description must characterize the return value, and it does ('plain verdict with a confidence level', summary only). For a one-parameter, read-only tool this is nearly complete; only minor details such as behavior when a product name is ambiguous are unaddressed.

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?

There is a single parameter and the schema describes it at 100% coverage, including accepted formats (URL, slug, product name) and length limits. The description adds nothing about the product argument, so the baseline of 3 applies when the schema carries the full burden.

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 names a specific operation: comparing a product's lowest in-stock price against Drop Beacon's observed range (90-day low, all-time low, high, watch duration) and returning a verdict plus confidence. That is concrete enough for an agent to know exactly what the tool produces. It doesn't explicitly contrast itself with siblings like top_deals or find_offers, so it stops short of a 5.

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 implied rather than stated: you call it when you have one product and want a deal judgement. The clause 'Summary only; it does not return the full price history' is a useful negative constraint that steers an agent away from expecting history, but no alternative tool is named and no preconditions are given.

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