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

Beyond the annotations (readOnlyHint=true, openWorldHint=true), the description adds meaningful operational detail: one GET, 5 s timeout, final URL after redirects, headers as served, and the full status envelope with ok/not_applicable/timeout/error variants. This gives the agent accurate expectations for side effects and failure modes.

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?

Every sentence carries useful information: purpose, what is returned, timeout, sibling alternative, and response status semantics. The purpose is front-loaded and the response format is compactly documented, making the description dense yet easily parseable.

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 tool with one well-documented parameter, no output schema, and read-only/external-safe annotations, this description covers what an agent needs: what headers are returned, how redirects are handled, timeout behavior, and how to interpret each status value. It also points to the sibling for redirect hops, making the surrounding toolset context clear.

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 already provides 100% coverage for the single parameter, including rejecting IPs, ports, paths, and protocol prefixes. The description adds no new parameter-level meaning—it references <domain> but does not clarify or extend beyond the schema, so the baseline 3 is appropriate.

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: "Fetch https://<domain>/ and return every response header," and lists the exact security headers an agent should look for. It also explicitly distinguishes itself from dossier_redirects by noting that redirect hops are handled there, so there is no sibling ambiguity.

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 clearly states when to use the tool: to review response security headers, and gives an explicit alternative: "For the redirect hops themselves use dossier_redirects." It also provides decision guidance on interpreting results, such as "Treat not_applicable as a finding and error as unknown," which helps the agent decide how to consume the output.

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