scan_url

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

With no annotations provided, the description carries the full burden and does a good job: it discloses the asynchronous behavior (immediate UUID return, 10-30 second completion), the API key requirement, and the visibility values. It lacks details on permission side-effects or potential failures, but overall it is notably transparent for a submission tool.

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 compact, front-loaded with the action, and every sentence contributes value: purpose, behavior, alternative tool, and key constraints. No filler or redundancies.

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's moderate complexity and the existence of an output schema, return values don't need explaining. The description covers the core purpose, async behavior, alternative, and the most critical parameters. However, it leaves several parameters unexplained and does not mention how the scan result will be retrieved, such as via get_scan_result, which would improve completeness.

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?

Input schema coverage is 0%, so the description must compensate, but it only explains two of six parameters: visibility (enum) and country (ISO code). The url, tags, referer, and user_agent parameters are not described, leaving the agent to infer their meaning from names and purpose. This partial compensation meets a minimum viable level but not more.

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 primary action: 'Submit a URL to urlscan.io for scanning.' It further specifies the immediate return with a UUID and distinguishes itself from the sibling tool scan_and_wait, making the purpose unambiguous and specific.

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?

Explicitly directs users to use scan_and_wait instead when they want the finished result in a single call, directly addressing when to use this tool vs. an alternative. Also provides temporal context (10-30 second scan duration) that helps select this async option.

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