C Claude Code Internals
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Tools

Claude Code has 45 built-in tools organized into 9 categories. The system prompt explicitly instructs Claude to prefer dedicated tools over general Bash commands whenever possible.

35 built-in tools 9 categories 5 conditional tools

The dedicated tools rule

The system prompt explicitly tells Claude to use dedicated tools instead of Bash for common operations. This improves transparency and makes tool calls reviewable.

Instead of Use
cat / head / tail / sed Read
sed / awk Edit
echo > / heredoc Write
find / ls Glob
grep / rg Grep

All tools by category

Files

Read, write, edit and search the filesystem

6 tools
Read Write Edit Glob Grep NotebookEdit

Shell

Execute commands in the terminal

3 tools
Bash PowerShell REPL

Web

Fetch URLs and search the internet

2 tools
WebFetch WebSearch

Agents

Spawn and communicate with sub-agents

4 tools
Agent SendMessage TeamCreate TeamDelete

Planning

Enter plan mode and manage git worktrees

4 tools
EnterPlanMode ExitPlanMode EnterWorktree ExitWorktree

Tasks

Create and track work items in the current session

5 tools
TaskCreate TaskUpdate TaskStop TaskOutput TodoWrite

Scheduling

Create cron jobs and remote triggers

4 tools
CronCreate CronDelete CronList RemoteTrigger

UI

Interact with the user and invoke skills

3 tools
AskUserQuestion Brief SkillTool

MCP

Model Context Protocol: connect external tools

4 tools
MCPTool ListMcpResources ReadMcpResource McpAuth

Conditional tools (feature flags)

Some tools only appear when specific feature flags are enabled. They are not available in standard Claude Code installations.

SleepTool
PROACTIVE / KAIROS

Pauses execution in autonomous mode. Required when there is nothing useful to do. Claude must never respond without calling sleep.

CronTools
AGENT_TRIGGERS

CronCreate, CronDelete, CronList: only available when the scheduling feature flag is enabled.

MonitorTool
MONITOR_TOOL

Performance and observability monitoring. Behind a separate feature flag.

WebBrowserTool
WEB_BROWSER_TOOL

Full browser automation (beyond WebFetch). Available when the browser tool flag is on.

REPLTool
Internal Anthropic users only

Interactive REPL execution. Not available to external users.

i Bash is reserved for the rest
Bash is meant for system commands and operations that have no dedicated tool. If Claude reaches for Bash to read a file or search code, it's not following its own prompt rules. You can remind it by saying "use the Read/Grep tool directly".