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

Annotations already mark the tool as read-only and non-destructive. The description adds API-key scoping ('available to your API key') and clarifies that it returns valid retailer IDs, which is useful behavioral context beyond the annotations. It does not describe the output shape or pagination, but this is a simple zero-parameter list operation.

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 sentences with no filler. The first states the action and scope; the second provides the workflow instruction. Every word 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?

For a zero-parameter discovery tool, the description covers what the tool does, the API-key scope, and how to use it in the larger workflow. It does not explicitly document the return format, but the stated purpose of discovering valid retailer IDs is enough for an agent to invoke it correctly.

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 tool has zero parameters, so there is nothing for the description to compensate for. The schema coverage is effectively 100%, and the description's mention of API-key scoping is sufficient context.

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: 'List all retailers available to your API key.' It also explains the tool's role as a discovery step for retailer IDs, which distinguishes it from sibling tools like search_retailer_products and get_retailer_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?

Provides explicit guidance: 'Always call this first to discover valid retailer IDs before searching products.' This tells the agent when to use the tool and what to do with the result, leaving no ambiguity about its role in the workflow.

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