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

Annotations already cover read-only and idempotent behavior, so the description adds valuable context by disclosing the exact cost ('0.0001 XNO in Nano via x402') and the structured return shape. It does not mention rate limits or failure modes, but the cost disclosure is a meaningful addition beyond 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?

The description is three short, front-loaded sentences with no filler. Each sentence earns its place: the operation, the output shape, and the cost. It is concise while still conveying essential information.

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?

With one fully documented parameter, an output schema, and annotations covering safety and idempotency, the description only needs to add engine, result shape, and cost—which it does. Nothing critical for invoking the tool is missing.

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 describes q as a 'Search query string to run through the web search backend.' The description adds the DuckDuckGo engine context, but it does not materially enrich parameter semantics beyond what the schema provides. This aligns with the baseline of 3 for high schema coverage.

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 states a specific verb and resource: 'Web search via DuckDuckGo.' It also clarifies the result type ('structured results with titles, URLs, and snippets'), which clearly distinguishes it from sibling tools like check_url_status or domain_info. The purpose is unmistakable.

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 clearly implies when to use the tool: whenever a DuckDuckGo-powered web search is needed. It does not explicitly name excluded cases or alternatives, but 'Web search via DuckDuckGo' is a clear usage context that separates it from URL/domain checking tools.

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