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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds valuable context: 'Free' (financial implication), 'does not create a purchase' (side-effect), and 'running its demo in a sandbox with no network access' (security/network isolation). This goes well beyond the annotations, which only indicate safety.

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, front-loaded with the core purpose. Every sentence adds unique information: what it does, sandbox behavior, cost, and absence of purchase side-effect. No wasted words.

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 simple 1-parameter tool with an output schema, the description covers key aspects: purpose, cost, side-effects, sandbox isolation, and conditionality of demo (only when seller supplies one). No major gaps remain, and the output schema handles return value details.

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%, with productId described as 'Id of the product to preview. Required.' The tool description adds no parameter-specific meaning beyond the schema, aside from implying a single product via 'one product'. Baseline 3 is appropriate as the schema already documents the parameter fully.

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 clearly states the tool's function: 'Inspect one product before buying', with a specific verb and resource. It differentiates from siblings like marketplace.purchase by explicitly noting 'does not create a purchase' and from search by focusing on a single product.

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?

Provides clear context: use before buying, and notes it is free and non-purchasing. It does not explicitly name alternative tools like marketplace.search or sandbox.check, but the 'before buying' and 'does not create a purchase' phrasing gives implicit usage boundaries. An explicit alternative would elevate it to 5.

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