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

Annotations already mark this as a read-only, non-destructive operation. The description adds useful context by specifying that the count is 'live items,' implying that inactive or deleted items may exist and are excluded from the count. This goes beyond what the annotations provide.

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 two sentences with no filler. The first sentence front-loads the action and output fields, and the second gives immediate guidance on how to use the result. Every sentence earns its place.

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?

Given the tool has zero parameters, read-only annotations, and an output schema, the description is fully sufficient for an agent to know when to call it and what it will receive. It also ties the result to downstream item tools, closing the loop on practical usage.

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?

With zero parameters and 100% schema coverage, there is little for the description to add. The absence of parameter documentation is appropriate, and the description correctly implies a parameterless call that lists all named lists without filters.

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 identifies the tool as listing named shopping lists and enumerates the exact fields returned (id, name, default flag, live item count). It also differentiates itself from sibling tools like list_shopping_list_items by framing this as resolving shoppingListId for the item tools.

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 phrase 'Use this to resolve a shoppingListId for the shopping list item tools' explicitly tells the agent when and why to invoke this tool. It lacks a formal when-not-to-use statement, but the purpose is unambiguous and strongly positions it against its siblings.

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