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

Beyond the readOnly and idempotent annotations, the description discloses that the full URL, including query and fragment, is shared with VTAI and VirusTotal, that the indicator is normalized, that query quota applies, and that unknown stays unknown. This is substantial behavioral context an agent needs before calling.

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 four short sentences, front-loaded with the core action, followed by relevant caveats and an alternative. Every sentence contributes unique information: scope, privacy, alternative, and normalization/quota behavior. There is no redundancy.

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 lookup without an output schema, the description covers the purpose, behavior, privacy implications, quota effects, and alternative tool enough for an agent to decide and invoke correctly. The 'Unknown stays unknown' statement clarifies the no-side-effect nature of the lookup.

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 schema provides only a title for the single `url` parameter and 0% description coverage. The tool description compensates by clarifying the expected input is an HTTP(S) URL, that the full URL with query/fragment is transmitted, and that normalization applies. It does not give explicit syntax examples, but for a single parameter this is a meaningful addition over 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 opens with a specific verb and resource: 'Look up existing intelligence for an HTTP(S) URL'. It also explicitly states what the tool does not do ('without visiting or submitting it'), distinguishing it from sibling submission tools and other report 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?

It gives a clear alternative with the exact condition: 'use get_domain_report when domain scope is sufficient'. It also warns against sending secret-bearing URLs, which is practical when-to-use guidance. The 'without visiting or submitting' phrase separates it from submission-oriented siblings.

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