check_portCheck from the internet whether TCP ports of a public host are open, closed or filtered. Use to verify firewall / security group rules, or why a service is reachable locally but not from outside. Only public addresses are allowed.
| Name | Required | Description | Default |
|---|---|---|---|
| host | Yes | Public hostname or IP | |
| ports | Yes | Comma-separated ports, e.g. 22,443 |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover readOnly and open-world behavior. The description adds real context beyond them: the three possible port states (open/closed/filtered) and the constraint that only public addresses are allowed. It omits rate limits and what error a private host produces, keeping it out of the 5 band.
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?
Three short sentences, front-loaded with the verb and outcome set, followed by usage and then the key constraint. No filler or redundancy.
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 helpfully defines the return vocabulary (open/closed/filtered) and the public-address restriction. It leaves the error behavior for non-public input unstated, which is the only meaningful gap for a 2-param tool.
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% — host is documented as a public hostname/IP and ports as a comma-separated list with an example. The description's 'public addresses only' adds a constraint but no new syntax or format detail, so the baseline of 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?
States a specific verb (check), resource (TCP ports of a public host), and the outcome taxonomy (open, closed, filtered), and scopes it to internet-origin checks. This clearly distinguishes it from siblings like check_dns, check_http, or ip_lookup.
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?
Gives concrete when-to-use triggers: verifying firewall/security-group rules and diagnosing a service reachable locally but not externally. It does not name sibling tools as alternatives, so it falls just short of the top band.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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