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

Annotations already declare the tool as read-only, open-world, idempotent, and non-destructive. The description adds useful behavioral context beyond that: it explains that results include verified agent endpoints, shipping eligibility, robots.txt-readable retailers, and Shopify cross-store search, which helps the agent understand the shape and nature of the response.

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 front-loaded with the core question and answer, followed by a clear 'Use when' cue and a compact example. Every sentence adds value without repeating structured data unnecessarily.

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?

No output schema exists, so the description appropriately explains what the tool returns. It covers the main query and country parameters and the behavioral context, though it leaves minor parameters like limit and agent_checkout_only to the schema.

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 80%, so the schema already documents most parameters. The description reinforces the meaning of 'query' and 'country' ('for my human's country', 'Any language') but does not add syntax or context for limit, category, or agent_checkout_only beyond what the schema 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 states a specific verb and resource ('Where can I shop for this product') and goes further to specify what is returned: agent-verified stores, UCP MCP endpoints, shipping eligibility, and big retailers readable by agents. This scope is clearly distinguishable from sibling tools like store_details and list_store_categories.

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?

It gives a direct 'Use when' cue ('your user wants to buy something') and a concrete example with query and country. However, it does not explicitly name alternatives or exclusions, such as when to use list_store_categories or store_details instead.

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