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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered. The description adds genuinely new behavioral context: the response shape changes based on whether product/channel are supplied, which an agent cannot infer from annotations alone.

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 tightly packed sentences with no filler; the core enumeration comes first, then the calling modes, then the downstream hand-off. Every clause carries information an agent needs.

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?

An output schema exists, so return values need not be restated, and the description covers the only ambiguity an agent faces—what changes when arguments are omitted or supplied. Nothing essential is missing for a 3-optional-param read tool.

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 schema already documents each enum. The description nonetheless adds value by explaining the conditional relationship between parameters and results (product unlocks regions/currencies, channel refines it), which is semantics beyond per-field docs.

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 names a specific verb (List) and enumerates the exact resources returned: products, sales channels, plan keys, billing intervals, regions. This immediately distinguishes it from the price-comparison siblings, which all consume these keys rather than produce them.

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 explicitly states two calling modes: bare for an overview, or with a product (and optionally a channel) to get region codes and currencies. It also tells the agent to feed the returned keys into 'the other tools,' establishing this as a prerequisite step. It stops short of naming which sibling to call next, so a 4 rather than 5.

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