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

Annotations already cover readOnly/openWorld safety, so the description adds real value beyond them: it discloses credential-free auth, the upstream data source (the store's own recommendation API), the upstream rejection behavior for a mismatched product_type, and the cost of the extra lookup when omitting product_type. It omits return-format details, but those are already carried by the output schema.

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?

Front-loads the purpose and keeps the guidance tight, but spends two sentences echoing Country/Locale defaults that the schema already documents, which is slight redundancy.

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 an output schema present, return values need not be explained, and the description covers purpose, type constraint, pagination, locale defaults, and the sibling alternative. Nothing critical for correct invocation is missing.

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 baseline is 3. The description largely restates parameter defaults (Country US, Locale en-US) already in the schema, though it adds the 'mismatched value is rejected upstream' nuance for product_type, which is marginally beyond the schema.

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 and resource ('Returns products related to a seed product id, paginated') and names a sibling (microsoftstore_recommended) that it is not. An agent can distinguish it from the recommendation-shelf tool without opening either 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 explicit when-to guidance for the product_type parameter (omit to auto-resolve, pass explicitly to skip the extra lookup) and names the alternative tool for default recommendations. It stops short of a full 'use this when X, use recommended when Y' routing rule, but the context is clear.

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