Development

Regex Debugger

Step through how a regular expression matches a string position by position: visualize match attempts, partial successes, backtracks, and captures — a learning tool for understanding regex behavior, not just the final result

interactive· Interactive resultOpen tool

Quick start

Call this tool from your code in three languages.

cURL

curl -X POST 'https://api.elysiatools.com/en/api/tools/regex-debugger' \
  -H 'Content-Type: application/json' \
  -d '{"pattern":"\\d+","flags":"g","testText":"Order 42 ships in 7 days"}'

API reference

Send a POST request with your inputs as JSON. File parameters require a separate upload first.

Endpoint

HTTP

POST https://api.elysiatools.com/en/api/tools/regex-debugger

Parameters

Name	Type	Required	Description
pattern	text	No	—
flags	text	No	—
testText	textarea	No	—

Response format

Interactive result

JSON

{
  "result": "Initial display content",
  "interactive": true,
  "components": [
    {
      "type": "timer",
      "id": "timer1",
      "config": {
        "label": "Countdown",
        "duration": 60
      }
    }
  ],
  "state": {
    "key": "value"
  },
  "actions": [
    {
      "type": "start",
      "id": "start-btn",
      "label": "Start"
    }
  ],
  "styles": "/* Custom CSS */",
  "scripts": "/* Client-side scripts */",
  "error": "Error message (optional)",
  "message": "Notification message (optional)",
  "metadata": {
    "key": "value"
  }
}

MCP integration

Add this tool to your Model Context Protocol server so AI agents can list and call it.

Server configuration

Add this block to your MCP client configuration:

mcp.json

{
  "mcpServers": {
    "elysiatools-regex-debugger": {
      "name": "regex-debugger",
      "description": "Step through how a regular expression matches a string position by position: visualize match attempts, partial successes, backtracks, and captures — a learning tool for understanding regex behavior, not just the final result",
      "baseUrl": "https://api.elysiatools.com/mcp/sse?toolId=regex-debugger",
      "command": "",
      "args": [],
      "env": {},
      "isActive": true,
      "type": "sse"
    }
  }
}

List available tools

After connecting to the SSE endpoint, list the exposed tools:

tools/list

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/list"
}

Call this tool

Invoke the tool by its id, passing arguments built from its parameters:

tools/call

{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "tools/call",
  "params": {
    "name": "regex-debugger",
    "arguments": {
  "pattern": "\\d+",
  "flags": "g",
  "testText": "Order 42 ships in 7 days"
}
  }
}

Chain multiple tools in one session with a comma-separated toolId list, e.g. /mcp/sse?toolId=png-to-webp,jpg-to-webp,gif-to-webp (max 20).

Questions or issues? Contact [email protected]

Browse tools Open tool

Name

Type

Required

Description

pattern

text

—

flags

text

—

testText

textarea

—

{ "result": "Initial display content", "interactive": true, "components": [ { "type": "timer", "id": "timer1", "config": { "label": "Countdown", "duration": 60 } } ], "state": { "key": "value" }, "actions": [ { "type": "start", "id": "start-btn", "label": "Start" } ], "styles": "/* Custom CSS */", "scripts": "/* Client-side scripts */", "error": "Error message (optional)", "message": "Notification message (optional)", "metadata": { "key": "value" } }

{ "mcpServers": { "elysiatools-regex-debugger": { "name": "regex-debugger", "description": "Step through how a regular expression matches a string position by position: visualize match attempts, partial successes, backtracks, and captures — a learning tool for understanding regex behavior, not just the final result", "baseUrl": "https://api.elysiatools.com/mcp/sse?toolId=regex-debugger", "command": "", "args": [], "env": {}, "isActive": true, "type": "sse" } } }

{ "jsonrpc": "2.0", "id": 2, "method": "tools/call", "params": { "name": "regex-debugger", "arguments": { "pattern": "\\d+", "flags": "g", "testText": "Order 42 ships in 7 days" } } }