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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the bar is lower. The description adds real value beyond them by disclosing the data source (HackerTarget) and the specific payload contents. It omits rate limits, error behavior, and what happens with unreachable hosts, keeping it out of 5 territory.

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?

One compact paragraph, front-loaded with the trigger phrases before the technical explanation, so nothing buries the purpose. The four quoted example queries consume space but earn it by aiding intent matching; slightly dense but well-structured.

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 no output schema, the description compensates by enumerating the return fields (status line, Server, Location, HSTS, CSP). For a single-parameter read tool whose annotations carry the safety profile, an agent has everything needed to select and invoke it correctly.

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?

There is a single parameter with 100% schema description coverage, so the schema already defines 'target' with hostname/URL examples. The description's bracketed '[site]'/'[X]' placeholders loosely reinforce this but add no format or syntax detail beyond the schema. Baseline 3 applies.

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 (HTTP response headers fetched by HackerTarget) and enumerates exactly what comes back: status line, Server, redirect Location, HSTS, CSP. The leading example queries ('what server runs [X]', 'does [site] redirect') let an agent map user intent directly, and the resource is clearly distinct from siblings like dns_lookup or whois.

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 clear usage context ('fingerprint a stack or audit header hygiene without loading the page yourself') plus four concrete trigger phrases, which is strong when-to-use guidance. It stops short of naming an alternative or an explicit when-not-to-use (e.g. vs dns_lookup or whois), so it is a 4 rather than a 5.

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