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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely non-redundant context: the exact 16-port coverage ceiling (so the agent knows MySQL-alt or 6379 is not checked), the return object shape, and an auth precondition. It omits scan duration/timeouts and any rate limiting.

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 scope, then return shape, then when-to-use. The long port enumeration is verbose but each entry carries real information about coverage. Auth requirement is tacked on at the end rather than placed with prerequisites.

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?

There is no output schema, but the description compensates by describing the returned { domain, ip, openPorts[], closedPorts[] } shape, and it discloses the auth precondition. Only the temporal aspect (how long a scan takes, whether results are cached) is unaddressed.

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?

Schema coverage is 100% for the single required 'domain' parameter, which already includes an example. The description confirms the domain-based scope but adds no format, normalization, or validation nuance beyond the schema. 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?

States a specific verb and resource (scan common TCP ports on a domain) and immediately bounds the scope to 16 enumerated ports with their service names. An agent can distinguish it from check_ssl, check_uptime, or check_security_headers without opening any schema.

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?

Explicitly lists the triggering intents: 'what services are running on a server', 'whether a specific port is open', or 'check firewall exposure'. It also states the prerequisite that the customer must be signed in. It does not name a sibling alternative, so it stops short of a 5.

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