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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety and non-determinism are covered. The description adds that it returns an indexed score and a breakdown, but does not detail what signals are included or how results might vary—which is partially mitigated by openWorldHint. It provides marginal extra context without contradicting 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?

A single, tightly-phrased sentence that front-loads the core output (score and signal breakdown) and the scope (single listing). No filler or redundant phrasing; every word contributes.

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 sufficiently outlines what is returned (score range and a signal breakdown) and the input scope. It could mention that the breakdown is structured per signal, but for a simple two-parameter read-only tool with annotations, this is nearly complete. Slight gap on output structure prevents a 5.

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 'retailer' (enum) and 'product_id' (with format example) documented. The description adds no extra meaning about parameters—it doesn't explain what 'product_id' refers to beyond the schema mention of 'Native retailer product ID.' Baseline of 3 is appropriate since the schema carries the semantic load.

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 states a specific verb ('Return') and a clearly defined resource: a 0–100 marketplace-evidence score plus the signal breakdown for a single retailer listing. It is unambiguous and distinguishes from the sibling 'compare_products' by explicitly scoping to one listing.

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 correctly implies this is for a single listing's trust evaluation, but it never states when an agent should use it versus the sibling 'compare_products' (e.g., for comparison tasks). No explicit exclusions or alternative routing are provided, so usage context is left to inference.

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