diff --git a/README.md b/README.md
index cce4cbb..7331dca 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # Sidekick
 
-Sidekick is a versatile agentic framework written in Go 1.25. It provides a robust architecture for building AI assistants with hierarchical orchestration, native Model Context Protocol (MCP) integration, and a rich terminal user interface (TUI).
+Sidekick is a simple but versatile agentic framework written in Go 1.25. It provides a robust architecture for building AI assistants with hierarchical orchestration, native Model Context Protocol (MCP) integration, and a rich terminal user interface (TUI).
 
 ## Features
 
@@ -9,8 +9,35 @@ Sidekick is a versatile agentic framework written in Go 1.25. It provides a robu
 *   **Intelligent Buffering:** Automatically buffers large tool outputs to prevent context window exhaustion, returning file pointers for significant payloads.
 *   **Rich Terminal UI:** A beautiful, responsive TUI built with Charmbracelet's BubbleTea and Lipgloss, featuring status bars, role-based formatting, and dynamic viewports.
 *   **Advanced Prompt Templating:** Define complex, multi-line system prompts using TOML. Support for Go's `text/template` engine allows you to compose modular prompts from reusable snippets.
+*   **Internal Tools:** Built-in tools for file I/O (`read_file`, `write_file`, `grep_file`, `edit_file`) and an optional, secure `shell_exec` tool for running POSIX shell commands.
 *   **Configuration Driven:** Easily configure models, agents, tools, and MCP servers via a declarative `config.toml` file.
 
+## Internal Tools
+
+Sidekick includes a set of internal tools that are always available to agents. These tools provide common file operations and system access.
+
+### File Tools
+- `read_file`: Read a file with optional line windowing.
+- `write_file`: Overwrite a file with new content.
+- `grep_file`: Regex search with surrounding context.
+- `edit_file`: Replace a string or block of lines in a file.
+
+### shell_exec Tool
+
+The `shell_exec` tool allows an agent to run arbitrary POSIX shell commands and receive combined stdout/stderr output. 
+
+**Security Warning:** This tool is extremely powerful and potentially dangerous. It is **disabled by default** and must be explicitly enabled for each agent in `config.toml`.
+
+To enable `shell_exec` for an agent, add `enable_shell_exec = true` to its configuration:
+
+```toml
+[agents.coordinator]
+role = "COORDINATOR"
+model_id = "default"
+enable_shell_exec = true # Security: explicitly enabled
+toolsets = ["filesystem"]
+```
+
 ## Installation
 
 ### Prerequisites
@@ -181,4 +208,4 @@ func main() {
 
 ## Credits
 
-Created by Luxferre in 2026, released into public domain with no warranties.
+Created by Luxferre in 2026, released into the public domain with no warranties.
diff --git a/agent.go b/agent.go
index dba720e..6cb88c0 100644
--- a/agent.go
+++ b/agent.go
@@ -24,6 +24,9 @@ func NewSidekick(config AgentConfig, model ModelConfig, extTools []ToolDefinitio
     ToolRegistry: make(map[string]ToolDefinition),
   }
   for name, tool := range DefaultInternalTools() {
+    if name == "shell_exec" && !s.Config.EnableShellExec {
+      continue
+    }
     s.registerTool(name, tool)
   }
   for _, tool := range extTools {
diff --git a/config.go b/config.go
index d0926dd..b1f3ed6 100644
--- a/config.go
+++ b/config.go
@@ -56,6 +56,7 @@ type AgentConfig struct {
   MaxIterations         int      `toml:"max_iterations"`
   Toolsets              []string `toml:"toolsets"`  // Allowed tool namespaces (MCP servers)
   Subagents             []string `toml:"subagents"` // Allowed subagent IDs
+  EnableShellExec       bool     `toml:"enable_shell_exec"`
   ToolResponseThreshold int      `toml:"-"`
 }
 
diff --git a/internal_tools.go b/internal_tools.go
index 0105474..edd4c98 100644
--- a/internal_tools.go
+++ b/internal_tools.go
@@ -3,6 +3,7 @@ package sidekick
 import (
   "fmt"
   "os"
+  "os/exec"
   "regexp"
   "strings"
 )
@@ -69,9 +70,43 @@ func DefaultInternalTools() map[string]ToolDefinition {
       Internal: true,
       Handler:  editFileHandler,
     },
+    "shell_exec": {
+      Name:        "shell_exec",
+      Description: "Run a POSIX shell command and return its combined stdout and stderr.",
+      Parameters: map[string]interface{}{
+        "type": "object",
+        "properties": map[string]interface{}{
+          "command": map[string]interface{}{"type": "string"},
+        },
+        "required": []string{"command"},
+      },
+      Internal: true,
+      Handler:  shellExecHandler,
+    },
   }
 }
 
+func shellExecHandler(args map[string]interface{}) (string, error) {
+  cmdStr, ok := args["command"].(string)
+  if !ok {
+    return "", fmt.Errorf("command is required")
+  }
+
+  cmd := exec.Command("sh", "-c", cmdStr)
+  output, err := cmd.CombinedOutput()
+
+  result := string(output)
+  if err != nil {
+    result = fmt.Sprintf("%s\nError: %v", result, err)
+  }
+
+  if result == "" {
+    return "(empty output)", nil
+  }
+
+  return result, nil
+}
+
 func readFileHandler(args map[string]interface{}) (string, error) {
   path, ok := args["path"].(string)
   if !ok {
diff --git a/internal_tools_test.go b/internal_tools_test.go
index 6b925c4..378b2c9 100644
--- a/internal_tools_test.go
+++ b/internal_tools_test.go
@@ -6,6 +6,23 @@ import (
   "testing"
 )
 
+func TestShellExecHandler(t *testing.T) {
+  // Success
+  got, err := shellExecHandler(map[string]interface{}{"command": "echo hello"})
+  if err != nil { t.Fatal(err) }
+  if strings.TrimSpace(got) != "hello" { t.Errorf("expected hello, got %s", got) }
+
+  // Failure
+  got, err = shellExecHandler(map[string]interface{}{"command": "ls /nonexistent-file-path-that-should-not-exist"})
+  if err != nil { t.Fatal(err) }
+  if !strings.Contains(got, "Error:") { t.Errorf("expected error in output, got %s", got) }
+
+  // Empty
+  got, err = shellExecHandler(map[string]interface{}{"command": "true"})
+  if err != nil { t.Fatal(err) }
+  if got != "(empty output)" { t.Errorf("expected empty output, got %s", got) }
+}
+
 func TestHashLine(t *testing.T) {
   line := "hello world"
   h1 := hashLine(line)
diff --git a/sidekick_test.go b/sidekick_test.go
index a2e07dd..e407e4b 100644
--- a/sidekick_test.go
+++ b/sidekick_test.go
@@ -79,6 +79,22 @@ func TestDelegation(t *testing.T) {
   if ans != "Coord done" { t.Errorf("expected Coord done, got %s", ans) }
 }
 
+func TestShellExecRegistration(t *testing.T) {
+  // Scenario 1: Disabled (default)
+  c1 := AgentConfig{ID: "a1", EnableShellExec: false}
+  a1 := NewSidekick(c1, ModelConfig{}, nil)
+  if _, ok := a1.ToolRegistry["shell_exec"]; ok {
+    t.Errorf("shell_exec should be disabled by default")
+  }
+
+  // Scenario 2: Enabled
+  c2 := AgentConfig{ID: "a2", EnableShellExec: true}
+  a2 := NewSidekick(c2, ModelConfig{}, nil)
+  if _, ok := a2.ToolRegistry["shell_exec"]; !ok {
+    t.Errorf("shell_exec should be enabled when EnableShellExec is true")
+  }
+}
+
 func TestTempFileCleanup(t *testing.T) {
   threshold := 10
   a := NewSidekick(AgentConfig{MaxIterations: 2, ToolResponseThreshold: threshold}, ModelConfig{}, nil)