Get a hostname

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

Annotations already declare readOnlyHint=true, so the description doesn't need to restate that. The description adds valuable behavioral context by disclosing a limitation: it does not reveal DNS resolution, and directs to diagnose_hostname. This goes beyond the annotation and helps the agent set expectations. It doesn't cover error behavior or return format, but for a read-only getter this is acceptable.

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 two sentences with zero waste. The primary purpose is front-loaded, and the limitation and alternative are placed second, so an agent scanning quickly gets the key information immediately. No redundant phrasing.

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 simple read-only tool with one parameter, no output schema, and readOnlyHint annotation, the description covers what the tool returns (status, cert mode), what it doesn't (DNS), and the alternative path. Nothing essential is missing for an agent to decide whether to call it and what to expect.

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 fully describes the single parameter id with a clear source ('from list_hostnames'), and schema coverage is 100%. The description adds no additional meaning about the parameter itself, only about the tool's output scope. Per the rubric, baseline 3 applies when schema covers parameters.

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: it retrieves a single hostname's status and certificate mode. It also differentiates from siblings by explicitly noting what it does NOT provide (where it points) and naming the alternative tool, making the purpose unambiguous.

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 gives clear guidance for when to use an alternative: if you need to know where the hostname points, use diagnose_hostname or resolve the name. It implies this tool is for status and certificate mode, and the sibling list_hostnames is for listing all, though it doesn't explicitly state 'use list_hostnames for multiple' or 'use this for a single hostname'. The guidance is clear enough for the common case.

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