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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so safety and idempotency are covered. The description adds genuinely new context beyond them: the test originates from external httpfy servers, which explains why results may differ from a local check, and it defines the three outcome states. It does not mention timeout behavior or rate limits, keeping it short of a 5.

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 sentence, front-loaded with the action and scoped by the qualifiers that matter (one port, public host, external vantage point). Nothing is redundant or 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?

For a two-parameter read-only tool with full schema coverage, rich annotations, and no output schema, this is close to complete: it conveys what is tested, from where, and what results mean. The remaining gap is operational detail such as expected latency or timeout, which is minor but would matter when interpreting a 'filtered' 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?

Schema coverage is 100%, with examples for both host and port, so the baseline is 3. The phrase 'a public host' does add a real constraint not present in the schema, but the description otherwise repeats parameter meaning rather than extending it with formats or edge cases.

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 names a specific verb (check), a specific resource (one TCP port on a public host), and enumerates the possible outcomes (open, closed, filtered). It also states the vantage point ('from httpfy servers on the internet'), which no sibling tool (ping, traceroute, dns_lookup) provides, so an agent can distinguish it without opening the 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?

Usage is implied: use this to test reachability of a single TCP port on an internet-facing host. There is no explicit when-to-use framing, no statement of when to prefer ping or traceroute instead, and no note that only one port can be tested per call. An agent can infer the context but must do the work itself.

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