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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false, so the safety profile is covered. The description adds useful behavior beyond annotations by explaining that free-text names are auto-resolved via search and that the data is current rather than historical. Nothing here contradicts the annotations.

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 dense sentences earn their place: the first states purpose and return contents, the second explains the two accepted input forms. There is no filler, repetition, or irrelevant detail.

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 one-parameter, read-only price lookup, this definition is complete. It names all return components, indicates how to resolve the input, and points to the relevant sibling search_device. Annotations cover the mutation/safety profile, and no output schema exists, so the description's return-value detail is appropriate.

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 100% and the schema already names and exemplifies the device parameter, so the baseline is met. The description adds meaningful nuance by specifying that free-text input is auto-resolved via search and that an exact slug from search_device is also accepted. It does not cover ambiguity or error handling, but it does add value.

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 identifies the resource clearly ('Current Swappa prices for a device') and enumerates the output fields: starting price, average price, breakdown by variant, active-listing average, and trade-in value. It does not use an explicit imperative verb like 'get' or 'retrieve', and it does not directly differentiate from the sibling sale_prices, but the meaning is unambiguous.

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 practical guidance on how to specify the device: free text auto-resolved via search, or an exact slug from search_device. It does not explicitly state when to choose this tool over sale_prices or other price-related siblings, but the 'Current Swappa prices' phrasing provides clear contextual scope.

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