Identify which process is listening on a TCP port, returning PID, name, and command line to reveal what service or app occupies that port.
Find what process is listening on a TCP port on this machine. Use when the user asks what service/app uses a port, what's on port X, or if a port is open (e.g. 8765 for the local Vela API). Returns PID, process name, and command line.
| Name | Required | Description | Default |
|---|---|---|---|
| port | Yes |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the bar is lower. The description adds value by stating the output: 'Returns PID, process name, and command line.' It does not cover edge cases like an unoccupied port or permission restrictions, but the safety profile is fully covered by annotations.
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 sentences, each earning its place: purpose, usage trigger, and return value. The example is embedded efficiently. No fluff or repetition.
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 one-parameter read-only tool with strong annotations, the description covers what it does, when to use it, and what it returns. The main missing piece is behavior when nothing is listening on the port, but this is a minor gap and likely inferable from the operation.
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 description coverage is 0%, so the description must compensate. It clarifies that the port is a TCP port and gives a concrete example (8765). For a single integer parameter, this is sufficient practical guidance, though it does not specify valid ranges or behavior on invalid input.
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?
Description opens with 'Find what process is listening on a TCP port on this machine,' naming a specific verb, resource, and scope. It clearly distinguishes itself from network connectivity tools like ping_host and process tools like list_processes, and includes a concrete example (Vela API port 8765).
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 provides explicit usage triggers: 'when the user asks what service/app uses a port, what's on port X, or if a port is open.' It stops short of naming alternative tools or exclusion criteria, but the use cases are concrete enough for an agent to route correctly.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.