localhost-mcp

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list_dev_servers

Read-onlyIdempotent

List every local development server currently running on a TCP port, showing framework, process info, and resource metrics.

Instructions

Read-only. Lists every local development server (next, vite, nuxt, remix, astro, rails, django, flask, express, deno, bun, etc.) currently LISTENING on a TCP port. For each: port, pid, process name, command line, working directory, project name, detected framework, uptime, memory (MB), CPU %, and owning user. Uses lsof on macOS/Linux and netstat on Windows; on Windows the cwd/framework fields are limited. Takes no arguments. Returns { count, servers[] }.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "list_dev_servers"
  }
}

Input Schema

Name	Required	Description	Default
No arguments

Output Schema

Name	Required	Description	Default
`count`	No
`servers`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv0.1.1May 11, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "count": {
+      "type": "number"
+    },
+    "servers": {
+      "items": {
+        "properties": {
+          "cmdline": {
+            "description": "Full command line, e.g. `next dev`.",
+            "type": "string"
+          },
+          "cpu_pct": {
+            "description": "Instantaneous CPU percent from `ps`.",
+            "type": "number"
+          },
+          "cwd": {
+            "description": "Working directory of the process (best-effort; may be empty on Windows).",
+            "type": "string"
+          },
+          "framework": {
+            "description": "Detected framework, e.g. `next.js`, `vite`, `rails`; `unknown` if not recognised.",
+            "type": "string"
+          },
+          "memory_mb": {
+            "description": "Resident set size in MB.",
+            "type": "number"
+          },
+          "pid": {
+            "type": "number"
+          },
+          "port": {
+            "type": "number"
+          },
+          "process": {
+            "description": "Process name, e.g. `node`, `python`.",
+            "type": "string"
+          },
+          "project_name": {
+            "description": "Basename of `cwd`, or the npm package name when detected.",
+            "type": "string"
+          },
+          "uptime_seconds": {
+            "type": "number"
+          },
+          "user": {
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "type": "array"
+    }
+  },
+  "type": "object"
+}

First observedv0.1.0May 9, 2026

TDQS

A4.5/5.0

Behavior5/5

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

The description adds significant behavioral context beyond annotations: it is read-only, uses lsof/netstat based on OS, notes Windows limitations on cwd/framework fields, and details the full output schema. Annotations confirm read-only, and no contradictions exist.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is three sentences with no fluff. It starts with the purpose, lists output fields, and ends with platform details and return structure. Every sentence earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a no-parameter tool, the description is exhaustive. It covers platform differences, limitations, output format, and all fields. The output schema exists and is described. No gaps remain.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

There are no parameters; the description correctly states 'takes no arguments'. With 0 parameters, baseline is 4, and the description adds no extra param information but confirms the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool lists local development servers listening on TCP ports, with a specific verb 'lists' and resource 'dev servers'. It includes a long list of frameworks and distinguishes itself from siblings like find_zombies or kill_server by focusing on active listening servers.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage when one wants to enumerate dev servers, but does not explicitly state when to use it over alternatives like port_info or port_conflict. No exclusion criteria or alternative tool names are mentioned.

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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