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

Annotations mark this as read-only and closed-world, and the description adds substantial behavioral context: it returns one of three verdicts (reaches, cannot_reach, unknown) rather than raw data, and lists the kinds of evidence involved. This goes well beyond what annotations alone convey.

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 organized into a clear intro, an explicit usage section, and a price line. It is slightly longer than necessary and some phrasing is redundant ('not just data' with 'verdict'), but every section earns its place and key information 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?

For a two-parameter read-only tool with no output schema, the description is effectively complete: it explains when to call, what data is considered, what verdict values will be returned, and the cost. An agent can decide to invoke or avoid this tool without needing more context.

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?

The schema already fully documents both parameters with examples and a pattern, so the description does not need to add much. The description loosely refers to 'storefront' and 'destination,' matching the store and destination fields, but adds no parameter-level meaning 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?

The description clearly states the tool's function: determining whether one storefront can serve one destination and returning a verdict. It enumerates concrete inputs (shipping zones, currency, cards, buyer reports, reach changes), which makes the tool's purpose distinguishable from vague sibling names like find, watch, or capabilities.

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 gives an explicit trigger: call when a store is already in mind and about to spend real money. It does not name specific siblings as alternatives or explicitly state when not to use it, but the usage context is clear enough to guide selection.

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