diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..9256b31
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+temp/*
+vendor/*
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..9354a6e
--- /dev/null
+++ b/README.md
@@ -0,0 +1,40 @@
+# Slack messaging tools
+
+![GitHub release](https://img.shields.io/github/release/FrancoisChaumont/slack-api-tools.svg)
+[![contributions welcome](https://img.shields.io/badge/contributions-welcome-brightgreen.svg?style=flat)](https://github.com/FrancoisChaumont/slack-api-tools/issues)
+
+Set of messaging tools using Slack API.
+
+## Requirements
+
+- [Composer](https://getcomposer.org)
+- PHP 7.4+
+
+## Installation
+
+```
+composer install
+```
+
+## Tools
+
+### Post a message to a channel
+See [post-message.php](post-message.php)
+```
+post-messsage.php -h/--help
+```
+See [README.post-message.md](READMEs/README.post-message.md) for more details.
+
+## Built with
+* Visual Studio Code
+
+## Authors
+* **Francois Chaumont** - *Initial work* - [FrancoisChaumont](https://github.com/FrancoisChaumont)
+
+See also the list of [contributors](https://github.com/FrancoisChaumont/db/graphs/contributors) who participated in this project.
+
+## License
+This project is licensed under the MIT License - see the [LICENSE.md](LICENSE.md) file for details.
+
+## Notes
+Todo: Add more tools
diff --git a/READMEs/README.post-message.md b/READMEs/README.post-message.md
new file mode 100644
index 0000000..b282e9e
--- /dev/null
+++ b/READMEs/README.post-message.md
@@ -0,0 +1,16 @@
+# Post a message to a Slack channel
+
+## Introduction
+
+**Create a Slack app**     
+See [create app](https://api.slack.com/start/overview#creating) documentation.
+
+Grant permission: `chat:write`
+
+**Sending a message**       
+See [sending message](https://api.slack.com/messaging/sending) documentation.
+
+**Find channel ID**     
+- In the Slack desktop app, right-click on the channel and select copy link. The last part of the URL is the ID.
+- In the browser version, navigate to the channel and check the URL. The last part of the URL is the ID.
+
diff --git a/composer.json b/composer.json
new file mode 100644
index 0000000..9ee0f51
--- /dev/null
+++ b/composer.json
@@ -0,0 +1,19 @@
+{
+    "name": "francoischaumont/slack",
+    "description": "Message functionalities through Slack API and apps",
+    "authors": [
+        {
+            "name": "Francois Chaumont",
+            "role": "main developer"
+        }
+    ],
+    "require": {
+        "php": "^7.4",
+        "guzzlehttp/guzzle": "^7.2"
+    },
+    "autoload": {
+        "psr-4": {
+            "FC\\Slack\\": "src/Slack/"
+        }
+    }
+}
diff --git a/composer.lock b/composer.lock
new file mode 100644
index 0000000..9d81a31
--- /dev/null
+++ b/composer.lock
@@ -0,0 +1,402 @@
+{
+    "_readme": [
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+                "source": "https://github.com/guzzle/promises/tree/1.4.0"
+            },
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+        },
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+                },
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+                    "src/functions_include.php"
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+            "notification-url": "https://packagist.org/downloads/",
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+                    "email": "mtdowling@gmail.com",
+                    "homepage": "https://github.com/mtdowling"
+                },
+                {
+                    "name": "Tobias Schultze",
+                    "homepage": "https://github.com/Tobion"
+                }
+            ],
+            "description": "PSR-7 message implementation that also provides common utility methods",
+            "keywords": [
+                "http",
+                "message",
+                "psr-7",
+                "request",
+                "response",
+                "stream",
+                "uri",
+                "url"
+            ],
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+                "issues": "https://github.com/guzzle/psr7/issues",
+                "source": "https://github.com/guzzle/psr7/tree/1.7.0"
+            },
+            "time": "2020-09-30T07:37:11+00:00"
+        },
+        {
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+            "version": "1.0.1",
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+                "reference": "2dfb5f6c5eff0e91e20e913f8c5452ed95b86621"
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+            },
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+                "psr/http-message": "^1.0"
+            },
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+                }
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+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
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+                    "homepage": "http://www.php-fig.org/"
+                }
+            ],
+            "description": "Common interface for HTTP clients",
+            "homepage": "https://github.com/php-fig/http-client",
+            "keywords": [
+                "http",
+                "http-client",
+                "psr",
+                "psr-18"
+            ],
+            "support": {
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+            },
+            "time": "2020-06-29T06:28:15+00:00"
+        },
+        {
+            "name": "psr/http-message",
+            "version": "1.0.1",
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+                "type": "git",
+                "url": "https://github.com/php-fig/http-message.git",
+                "reference": "f6561bf28d520154e4b0ec72be95418abe6d9363"
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+                    "Psr\\Http\\Message\\": "src/"
+                }
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+                    "homepage": "http://www.php-fig.org/"
+                }
+            ],
+            "description": "Common interface for HTTP messages",
+            "homepage": "https://github.com/php-fig/http-message",
+            "keywords": [
+                "http",
+                "http-message",
+                "psr",
+                "psr-7",
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+                "response"
+            ],
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+                "source": "https://github.com/php-fig/http-message/tree/master"
+            },
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+                "url": "https://github.com/ralouphie/getallheaders.git",
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+                "files": [
+                    "src/getallheaders.php"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Ralph Khattar",
+                    "email": "ralph.khattar@gmail.com"
+                }
+            ],
+            "description": "A polyfill for getallheaders.",
+            "support": {
+                "issues": "https://github.com/ralouphie/getallheaders/issues",
+                "source": "https://github.com/ralouphie/getallheaders/tree/develop"
+            },
+            "time": "2019-03-08T08:55:37+00:00"
+        }
+    ],
+    "packages-dev": [],
+    "aliases": [],
+    "minimum-stability": "stable",
+    "stability-flags": [],
+    "prefer-stable": false,
+    "prefer-lowest": false,
+    "platform": {
+        "php": "^7.4"
+    },
+    "platform-dev": [],
+    "plugin-api-version": "2.0.0"
+}
diff --git a/post-message.php b/post-message.php
new file mode 100644
index 0000000..f86a9b4
--- /dev/null
+++ b/post-message.php
@@ -0,0 +1,37 @@
+<?php
+
+namespace FC\Slack;
+
+ini_set("display_errors", true);
+ini_set("error_reporting", E_ALL);
+
+require 'vendor/autoload.php';
+require 'usage/post-message.usage.php';
+
+try {
+    // init options
+    if (!isset($options[OPTION_TOKEN])) { throw new \Exception("Missing option <token>!"); }
+    else { $appToken = $options[OPTION_TOKEN]; }
+    if (!isset($options[OPTION_CHANNEL])) { throw new \Exception("Missing option <channel>!"); }
+    else { $channel = $options[OPTION_CHANNEL]; }
+    if (!isset($options[OPTION_MESSAGE])) { throw new \Exception("Missing option <message>!"); }
+    else { $message = $options[OPTION_MESSAGE]; }
+
+    // init Guzzle client
+    $client = new \GuzzleHttp\Client();
+
+    // init Slack App
+    $slackApp = new \FC\Slack\SlackApp($appToken);
+
+    // post message
+    $r = $slackApp->postMessage($client, $channel, $message);
+    if ($r === true) {
+        exit(0);
+    } else {
+        throw new \Exception("Failed to post message: $r");
+    }
+
+} catch (\Exception $e) {
+    echo $e->getMessage() . PHP_EOL;
+    exit(1);
+}
diff --git a/src/Slack/SlackApp.php b/src/Slack/SlackApp.php
new file mode 100644
index 0000000..02f3b5d
--- /dev/null
+++ b/src/Slack/SlackApp.php
@@ -0,0 +1,60 @@
+<?php
+
+namespace FC\Slack;
+
+class SlackApp
+{
+    /** @var string POST_MESSAGE_URL URL where to send message to */
+    const POST_MESSAGE_URL = 'https://slack.com/api/chat.postMessage';
+
+    /** @var string $appToken Token of the interacting app */
+    private string $appToken;
+
+    /**
+     * Constructor
+     *
+     * @param string $appToken Token of the interacting app
+     */
+    public function __construct(string $appToken)
+    {
+        $this->appToken = $appToken;
+    }
+
+    /**
+     * Post a message to a channel
+     *
+     * @param \GuzzleHttp\Client $client Guzzle client to handle HTTP requests
+     * @param string $channelId ID of the channel to post the message to
+     * @param string $text Message to be posted
+     * @return bool|string true on success, HTTP response code + reason on failure
+     */
+    public function postMessage(\GuzzleHttp\Client $client, string $channelId, string $text)
+    {
+        $message = <<< EOS
+        {
+            "channel": "$channelId",
+            "text": "$text"
+        }
+        EOS;
+
+        $headers = [
+            'Authorization' => 'Bearer ' . $this->appToken,
+            'Content-type' => 'application/json'
+        ];
+
+        $response = $client->request(
+            'POST',
+            self::POST_MESSAGE_URL, [
+                'headers' => $headers,
+                'json' => json_decode($message, true)
+            ]
+        );
+
+        $code = $response->getStatusCode(); // 200
+        $reason = $response->getReasonPhrase(); // OK
+
+        if ($code == 200) { return true; }
+        else { return $code . " - " . $reason; }
+    }
+}
+
diff --git a/usage/post-message.usage.php b/usage/post-message.usage.php
new file mode 100644
index 0000000..d4f708e
--- /dev/null
+++ b/usage/post-message.usage.php
@@ -0,0 +1,53 @@
+<?php
+
+// retrieve the name of the file that includes this usage file
+define('INCLUDED_FILE', basename(get_included_files()[0]));
+
+// modify the description here below
+$whatItDoes = <<<EOS
+Post message to channel
+
+Exit code:
+    0 - message posted successfully to channel
+    1 - message posting failed
+EOS;
+
+$usageIntro = "What it does:\n\n    %s\n\nUsage: php %s %s\n";
+
+define('USAGE', sprintf($usageIntro, $whatItDoes, INCLUDED_FILE, sprintf(<<<EOS
+[options]
+
+Options:
+    -h/--help                               Show this help message and exit
+
+    -t/--token                              [REQUIRED] Slack app token
+    -c/--channel                            [REQUIRED] Slack channel ID
+    -m/--message                            [REQUIRED] Message to post to channel
+
+    php %1\$s 
+
+Example:
+    php %1\$s \
+        -t xoxb-123456 \
+        -c ABC123DEF45 \
+        -m "Message to be posted to channel"
+EOS, INCLUDED_FILE)));
+
+$shortOpts = 't:c:m:h';
+$longOpts = [
+    'token:',
+    'channel:',
+    'message:',
+    'help'
+];
+
+// set options
+$options = getopt($shortOpts, $longOpts);
+if (isset($options['h']) || isset($options['help'])) {
+    print USAGE;
+    exit;
+}
+
+define('OPTION_TOKEN', isset($options['t']) ? 't' : 'token');
+define('OPTION_CHANNEL', isset($options['c']) ? 'c' : 'channel');
+define('OPTION_MESSAGE', isset($options['m']) ? 'm' : 'message');