diff --git a/slackme/README.md b/slackme/README.md
index 92f91af..017f06a 100644
--- a/slackme/README.md
+++ b/slackme/README.md
@@ -61,3 +61,21 @@ $ slackme npm run long-build
      auth_provider_id = "slack"
    }
    ```
+
+## Examples
+
+### Custom Slack Message
+
+- `$COMMAND` is replaced with the command the user executed.
+- `$DURATION` is replaced with a human-readable duration the command took to execute.
+
+```hcl
+module "slackme" {
+  source = "https://registry.coder.com/modules/slackme"
+  agent_id = coder_agent.example.id
+  auth_provider_id = "slack"
+  slack_message = <<EOF
+👋 Hey there from Coder! $COMMAND took $DURATION to execute!
+EOF
+}
+```
diff --git a/slackme/main.test.ts b/slackme/main.test.ts
index 88b3a04..44db86a 100644
--- a/slackme/main.test.ts
+++ b/slackme/main.test.ts
@@ -1,15 +1,14 @@
+import { serve } from "bun";
 import { describe, expect, it } from "bun:test";
 import {
   createJSONResponse,
   execContainer,
-  executeScriptInContainer,
   findResourceInstance,
   runContainer,
   runTerraformApply,
   runTerraformInit,
   testRequiredVariables,
 } from "../test";
-import { serve } from "bun";
 
 describe("slackme", async () => {
   await runTerraformInit(import.meta.dir);
@@ -19,25 +18,6 @@ describe("slackme", async () => {
     auth_provider_id: "foo",
   });
 
-  const setupContainer = async (image = "alpine") => {
-    const state = await runTerraformApply(import.meta.dir, {
-      agent_id: "foo",
-      auth_provider_id: "foo",
-    });
-    const instance = findResourceInstance(state, "coder_script");
-    const id = await runContainer(image);
-    return { id, instance };
-  };
-
-  const writeCoder = async (id: string, script: string) => {
-    const exec = await execContainer(id, [
-      "sh",
-      "-c",
-      `echo '${script}' > /usr/bin/coder && chmod +x /usr/bin/coder`,
-    ]);
-    expect(exec.exitCode).toBe(0);
-  };
-
   it("writes to path as executable", async () => {
     const { instance, id } = await setupContainer();
     await writeCoder(id, "exit 0");
@@ -55,7 +35,7 @@ describe("slackme", async () => {
     expect(exec.exitCode).toBe(0);
     exec = await execContainer(id, ["sh", "-c", "slackme"]);
     expect(exec.stdout.trim()).toStartWith(
-      "slackme — Send a Slack notification when a command finishes",
+      "slackme — Send a Slack notification when a command finishes"
     );
   });
 
@@ -68,31 +48,122 @@ describe("slackme", async () => {
     expect(exec.stdout.trim()).toEndWith("some-url");
   });
 
-  it("curls url when authenticated", async () => {
-    let url: URL;
-    const fakeSlackHost = serve({
-      fetch: (req) => {
-        url = new URL(req.url);
-        if (url.pathname === "/api/chat.postMessage")
-          return createJSONResponse({
-            ok: true,
-          });
-        return createJSONResponse({}, 404);
-      },
-      port: 0,
+  it("default output", async () => {
+    await assertSlackMessage({
+      command: "echo test",
+      durationMS: 2,
+      output: "👨‍💻 `echo test` completed in 2ms",
     });
+  });
 
-    const { instance, id } = await setupContainer("alpine/curl");
-    await writeCoder(id, "echo 'token'");
-    let exec = await execContainer(id, ["sh", "-c", instance.script]);
-    expect(exec.exitCode).toBe(0);
-    exec = await execContainer(id, [
-      "sh",
-      "-c",
-      `SLACK_URL="http://${fakeSlackHost.hostname}:${fakeSlackHost.port}" slackme echo test`,
-    ]);
-    expect(exec.stdout.trim()).toEndWith("test");
-    expect(url.pathname).toEqual("/api/chat.postMessage");
-    expect(url.searchParams.get("channel")).toEqual("token");
+  it("formats multiline message", async () => {
+    await assertSlackMessage({
+      command: "echo test",
+      format: `this command:
+\`$COMMAND\`
+executed`,
+      output: `this command:
+\`echo test\`
+executed`,
+    });
+  });
+
+  it("formats execution with milliseconds", async () => {
+    await assertSlackMessage({
+      command: "echo test",
+      format: `$COMMAND took $DURATION`,
+      durationMS: 150,
+      output: "echo test took 150ms",
+    });
+  });
+
+  it("formats execution with seconds", async () => {
+    await assertSlackMessage({
+      command: "echo test",
+      format: `$COMMAND took $DURATION`,
+      durationMS: 15000,
+      output: "echo test took 15.0s",
+    });
+  });
+
+  it("formats execution with minutes", async () => {
+    await assertSlackMessage({
+      command: "echo test",
+      format: `$COMMAND took $DURATION`,
+      durationMS: 120000,
+      output: "echo test took 2m 0.0s",
+    });
+  });
+
+  it("formats execution with hours", async () => {
+    await assertSlackMessage({
+      command: "echo test",
+      format: `$COMMAND took $DURATION`,
+      durationMS: 60000 * 60,
+      output: "echo test took 1hr 0m 0.0s",
+    });
   });
 });
+
+const setupContainer = async (
+  image = "alpine",
+  vars: Record<string, string> = {}
+) => {
+  const state = await runTerraformApply(import.meta.dir, {
+    agent_id: "foo",
+    auth_provider_id: "foo",
+    ...vars,
+  });
+  const instance = findResourceInstance(state, "coder_script");
+  const id = await runContainer(image);
+  return { id, instance };
+};
+
+const writeCoder = async (id: string, script: string) => {
+  const exec = await execContainer(id, [
+    "sh",
+    "-c",
+    `echo '${script}' > /usr/bin/coder && chmod +x /usr/bin/coder`,
+  ]);
+  expect(exec.exitCode).toBe(0);
+};
+
+const assertSlackMessage = async (opts: {
+  command: string;
+  format?: string;
+  durationMS?: number;
+  output: string;
+}) => {
+  let url: URL;
+  const fakeSlackHost = serve({
+    fetch: (req) => {
+      url = new URL(req.url);
+      if (url.pathname === "/api/chat.postMessage")
+        return createJSONResponse({
+          ok: true,
+        });
+      return createJSONResponse({}, 404);
+    },
+    port: 0,
+  });
+  const { instance, id } = await setupContainer(
+    "alpine/curl",
+    opts.format && {
+      slack_message: opts.format,
+    }
+  );
+  await writeCoder(id, "echo 'token'");
+  let exec = await execContainer(id, ["sh", "-c", instance.script]);
+  expect(exec.exitCode).toBe(0);
+  exec = await execContainer(id, [
+    "sh",
+    "-c",
+    `DURATION_MS=${opts.durationMS || 0} SLACK_URL="http://${
+      fakeSlackHost.hostname
+    }:${fakeSlackHost.port}" slackme ${opts.command}`,
+  ]);
+  expect(exec.stderr.trim()).toBe("");
+  expect(url.pathname).toEqual("/api/chat.postMessage");
+  expect(url.searchParams.get("channel")).toEqual("token");
+  expect(url.searchParams.get("text")).toEqual(opts.output);
+};
diff --git a/slackme/main.tf b/slackme/main.tf
index ee67ae2..9eccfae 100644
--- a/slackme/main.tf
+++ b/slackme/main.tf
@@ -22,7 +22,7 @@ variable "auth_provider_id" {
 variable "slack_message" {
   type        = string
   description = "The message to send to Slack."
-  default     = "Your command completed!"
+  default     = "👨‍💻 `$COMMAND` completed in $DURATION"
 }
 
 resource "coder_script" "install_slackme" {
@@ -37,7 +37,7 @@ resource "coder_script" "install_slackme" {
     cat > $CODER_DIR/slackme <<INNER
     ${replace(templatefile("${path.module}/slackme.sh", {
   PROVIDER_ID : var.auth_provider_id,
-  SLACK_MESSAGE : urlencode(var.slack_message),
+  SLACK_MESSAGE : replace(var.slack_message, "`", "\\`"),
 }), "$", "\\$")}
 INNER
 
diff --git a/slackme/slackme.sh b/slackme/slackme.sh
index bafab4e..17f74ec 100644
--- a/slackme/slackme.sh
+++ b/slackme/slackme.sh
@@ -1,7 +1,10 @@
 #!/usr/bin/env sh
 
 PROVIDER_ID=${PROVIDER_ID}
-SLACK_MESSAGE="${SLACK_MESSAGE}"
+SLACK_MESSAGE=$(cat << "EOF"
+${SLACK_MESSAGE}
+EOF
+)
 SLACK_URL=$${SLACK_URL:-https://slack.com}
 
 usage() {
@@ -13,6 +16,43 @@ Example: slackme npm run long-build
 EOF
 }
 
+pretty_duration() {
+    local duration_ms=$1
+
+    # If the duration is less than 1 second, display in milliseconds
+    if [ $duration_ms -lt 1000 ]; then
+        echo "$${duration_ms}ms"
+        return
+    fi
+
+    # Convert the duration to seconds
+    local duration_sec=$((duration_ms / 1000))
+    local remaining_ms=$((duration_ms % 1000))
+
+    # If the duration is less than 1 minute, display in seconds (with ms)
+    if [ $duration_sec -lt 60 ]; then
+        echo "$${duration_sec}.$${remaining_ms}s"
+        return
+    fi
+
+    # Convert the duration to minutes
+    local duration_min=$((duration_sec / 60))
+    local remaining_sec=$((duration_sec % 60))
+
+    # If the duration is less than 1 hour, display in minutes and seconds
+    if [ $duration_min -lt 60 ]; then
+        echo "$${duration_min}m $${remaining_sec}.$${remaining_ms}s"
+        return
+    fi
+
+    # Convert the duration to hours
+    local duration_hr=$((duration_min / 60))
+    local remaining_min=$((duration_min % 60))
+
+    # Display in hours, minutes, and seconds
+    echo "$${duration_hr}hr $${remaining_min}m $${remaining_sec}.$${remaining_ms}s"
+}
+
 if [ $# -eq 0 ]; then
     usage
     exit 1
@@ -30,9 +70,18 @@ if [ $? -ne 0 ]; then
   exit 1
 fi
 
+START=$(date +%s%N)
 # Run all arguments as a command
 $@
+END=$(date +%s%N)
+DURATION_MS=$${DURATION_MS:-$(( (END - START) / 1000000 ))}
+PRETTY_DURATION=$(pretty_duration $DURATION_MS)
 
 set -e
+COMMAND=$(echo $@)
+SLACK_MESSAGE=$(echo "$SLACK_MESSAGE" | sed "s|\\$COMMAND|$COMMAND|g")
+SLACK_MESSAGE=$(echo "$SLACK_MESSAGE" | sed "s|\\$DURATION|$PRETTY_DURATION|g")
+
 curl --silent -o /dev/null --header "Authorization: Bearer $BOT_TOKEN" \
-    "$SLACK_URL/api/chat.postMessage?channel=$USER_ID&text=$SLACK_MESSAGE&pretty=1"
+    -G --data-urlencode "text=$${SLACK_MESSAGE}" \
+    "$SLACK_URL/api/chat.postMessage?channel=$USER_ID&pretty=1"