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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, indicating a safe, side-effect-free operation. The description adds valuable behavioral context by disclosing the API key requirement (external authentication) and enumerating the returned data fields. This goes beyond the annotations but could have been richer (e.g., note that it makes an external network call, potential rate limits), but for a read-only scan the key requirement is the most critical behavioral detail.

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 concise: two sentences and an example. The primary purpose is front-loaded, the output types are listed, and the API key requirement is stated without unnecessary detail. Every sentence earns its place, and the formatting is clean and scannable.

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 simple tool with two parameters and no output schema, the description covers the essential context: what it checks, what it returns, and the prerequisite API key. The return values are enumerated but not detailed in format (e.g., risk score range), yet for an agent to decide if this tool is suitable, the listed information is sufficient. The lack of explicit output schema is mitigated by listing the return fields, so the description is as complete as needed for this complexity level.

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%, with both `url` and `_apiKey` adequately described in the schema. The description adds a concrete example and clarifies that the API key is user-provided (BYO) with a pointer to the free tier, but this is marginal added value. The baseline for high schema coverage is 3, and the description does not substantially enrich parameter meaning beyond the schema.

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 states the tool's purpose: it performs a URL/malware safety scan, checking for phishing, malware, and spam. It names the specific output fields (risk score, domain reputation rank, content category, DNS validity, domain age) and includes an example invocation. This distinguishes it from sibling tools like check_email, check_ip, and check_phone, which focus on other entity types.

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 implicitly communicates when to use this tool: when a URL or domain needs a safety check. It also provides a clear prerequisite: the user must supply their own IPQualityScore API key, with a note about the free tier. However, it does not explicitly contrast with sibling tools or state when not to use it, though the distinct entity type (URL vs email/IP/phone) makes the intent clear.

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