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localhost-mcp

localhost-mcp

by HasanJahidul
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Local

port_conflict

Read-onlyIdempotent

Diagnose EADDRINUSE errors: identify the dev server blocking a port and get 5 free nearby alternatives.

Instructions

Read-only. Diagnoses an EADDRINUSE situation: given a port, returns the dev server currently blocking it plus 5 free alternative ports nearby. Use it when a listen EADDRINUSE error fires and you want both the culprit and a port to switch to.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "port": "<port>"
    },
    "name": "port_conflict"
  }
}

Input Schema

NameRequiredDescriptionDefault
portYesThe contended TCP port, e.g. 3000.

Output Schema

NameRequiredDescriptionDefault
portNo
blocked_byNoThe dev-server record holding the port (see list_dev_servers), or null if actually free.
alternativesNoUp to 5 nearby free ports.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changedv0.1.1
    • addedInput schema / properties / port / description
      Added value: +"The contended TCP port, e.g. 3000."
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
+  "properties": {
+    "alternatives": {
+      "description": "Up to 5 nearby free ports.",
+      "items": {
+        "type": "number"
+      },
+      "type": "array"
+    },
+    "blocked_by": {
+      "description": "The dev-server record holding the port (see list_dev_servers), or null if actually free.",
+      "type": [
+        "object",
+        "null"
+      ]
+    },
+    "port": {
+      "type": "number"
+    }
+  },
+  "type": "object"
+}
  2. First observedv0.1.0

TDQS

A4.3/5.0
Behavior4/5

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

Annotations already declare readOnlyHint, destructiveHint false, and idempotentHint true. The description adds that it returns the blocking server and free ports, which is useful context beyond the annotations. No contradictions.

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?

Two sentences: the first declares read-only behavior and functionality, the second provides usage guidance. No extraneous words; each 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 simple tool with one parameter and an output schema, the description fully covers purpose, trigger condition, and return value. No gaps remain.

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

Parameters3/5

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

Schema coverage is 100% for the single parameter. The description repeats the schema's description ('The contended TCP port, e.g. 3000.') without adding new meaning. Baseline 3 is appropriate since the schema already provides sufficient detail.

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 diagnoses an EADDRINUSE situation by returning the blocking dev server and 5 free alternative ports. Its verb 'diagnose' and resource 'port conflict' are specific, and it distinguishes itself from sibling tools (e.g., kill_server, find_zombies) that serve different purposes.

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

Usage Guidelines4/5

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

The description explicitly advises using this tool when a 'listen EADDRINUSE' error occurs, specifying the desired outcome (culprit and free ports). While it doesn't list alternatives or when not to use, the context is clear enough for an agent to decide.

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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