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

With no annotations, the description carries the full burden and does so richly: latency (15-45s, up to ~50s), shared 50/day budget, single-flight concurrency, retry guidance ('don't retry in a tight loop'), the render lane and its status enum, privacy exposure (full URL transmitted/logged/fetched), prompt-injection warning, and how to interpret unrendered results and service_range.

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?

Front-loaded with purpose, then usage, then behavioral caveats, and nearly every clause is information-dense. It is long, and a few details (the service_range explanation) sit at the tail and could be trimmed, but it is not padded.

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?

No output schema exists, so the description compensates by naming the returned fields (coverage, render.status, probability, analysis_failures, service_range) and how to read them. For a slow, rate-limited, actively-fetching tool, an agent has everything needed to call it correctly and interpret the result.

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?

Only one parameter with 100% schema description coverage, so the schema already documents it; the description's privacy note about preferring a bare domain largely restates the schema description. Baseline 3 is appropriate since the schema does the heavy lifting.

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?

States a specific verb+resource ('ACTIVE deep analysis of a URL') and immediately contrasts it with the sibling analyze_url ('which NEVER contacts the target'), so an agent can distinguish the two without opening either schema. The enumerated evidence types (HTTP, TLS, RDAP, nameservers, GeoIP) further pin down scope.

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?

Gives explicit when-to-use ('only when analyze_url's passive signals are inconclusive'), explicit when-not ('NOT a default first call'), and names the alternative plus the condition that selects it. Nothing about tool selection is left to inference.

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