Claude Code Tools Agents And Tasks

Claude Code Tools: Agents, Tasks, and Planning

These tools start subagents, send messages, track tasks, schedule work, and control plan mode and worktrees. Claude uses them to split a large job into parts. For example, Agent starts a subagent with its own context, and TaskCreate adds a step to the task list. The marks are explained on Tools.

Tools

Mark	Item	What It Does	How It Works	Where It Can Be Used	Read-Only	Parallel	Deferred	Source
✅	Agent	Starts a subagent (alias Task).	Parameters are listed in Agent Parameters.	Main session and subagents until the depth limit. At the limit only a fork keeps it.	✅	✅	❌	Tools Reference, Configure Permissions
✅	SubagentHandback	A subagent returns its final report to its caller.	message (string, required). alwaysLoad true. Not deferred. Only offered to a subagent that reports through it.	Subagents.	❌	❌	❌	Tools Reference, Create Custom Subagents
✅	SendMessage	Sends a message to a teammate, a named subagent, main, or a background agent.	to (string, required), summary (string, optional, label), message (string, required). In a build with notify_when_idle (boolean, optional) the field asks for one idle notice.	Main session and subagents.	✅	❌	✅	Tools Reference, Create Custom Subagents
✅ 🧪	ListAgents	Lists agents that SendMessage can reach.	channel and q (strings, optional, "not available in this build"). Alias ListPeers. The docs say cross-session messaging must be on. Not kept in background subagents.	Main session and foreground subagents.	✅	✅	❌	Tools Reference, Create Custom Subagents
✅	Skill	Runs a skill or slash command.	skill (string, required), args (string, optional).	Main session and subagents. Kept in background subagents.	❌	❌	❌	Tools Reference, Configure Permissions
✅ 🧪	TodoWrite	Writes the session checklist (legacy).	CLAUDE_CODE_ENABLE_TASKS=0 selects TodoWrite over the Task tools. A hidden server-side flag turns it on.	Main session and subagents. Kept in background subagents.	❌	❌	✅	Tools Reference, Create Custom Subagents
✅ 🧪	TaskCreate	Creates a task.	subject (string, required), description (string, required), activeForm (string, optional), metadata (object, optional). Default on models in the Task tool availability list.	Main session. Teammates keep them. Other subagents do not.	❌	❌	✅	Tools Reference, Create Custom Subagents
✅ 🧪	TaskGet	Reads a task.	taskId (string, required). A hidden server-side flag turns it on.	Same as TaskCreate.	✅	❌	✅	Tools Reference, Create Custom Subagents
✅ 🧪	TaskUpdate	Updates or deletes a task.	taskId (required), subject, description, activeForm, status (task status or deleted), addBlocks, addBlockedBy (string arrays), owner, metadata (null deletes a key).	Same as TaskCreate.	❌	❌	✅	Tools Reference, Create Custom Subagents
✅ 🧪	TaskList	Lists tasks.	No parameters. A hidden server-side flag turns it on.	Same as TaskCreate.	✅	❌	✅	Tools Reference, Create Custom Subagents
✅ 🧪	CronCreate	Schedules a prompt (recurring or once).	cron (5-field string, local time, required), prompt (string, required), recurring (boolean, default true, expires after a set number of days), durable (boolean, optional).	Main session. Teammates keep them.	❌	❌	✅	Tools Reference, Create Custom Subagents
✅ 🧪	CronDelete	Cancels a cron job.	id (string, required). A hidden server-side flag turns it on.	Same.	❌	❌	✅	Tools Reference, Create Custom Subagents
✅ 🧪	CronList	Lists cron jobs.	No parameters. A hidden server-side flag turns it on.	Same.	✅	❌	❌	Tools Reference, Create Custom Subagents
✅ 🧪	ScheduleWakeup	Schedules the next turn of a dynamic /loop.	delaySeconds (number, clamped to 60 to 3600), reason, prompt, stop (boolean), noop (boolean). All optional, the first three are required unless stop is true. shouldDefer:!1.	Main session.	❌	❌	❌	Tools Reference, Create Custom Subagents
✅ 🧪	Workflow	Runs a JavaScript workflow that orchestrates subagents.	script, name, scriptPath, args, resumeFromRunId. description and title are ignored. Alias RunWorkflow. CLAUDE_CODE_DISABLE_WORKFLOWS=1 turns it off. Removed from subagents.	Main session.	❌	❌	❌	Tools Reference, Create Custom Subagents
✅	EnterWorktree	Creates a git worktree and switches into it.	name (string, optional) or path (string, optional, an existing worktree). Not both. Not deferred when CLAUDE_CODE_SESSION_KIND is bg. Refused from a subagent with a cwd override.	Main session and subagents. Kept in background subagents.	❌	❌	✅	Tools Reference, Create Custom Subagents
✅	ExitWorktree	Leaves the worktree.	action (keep or remove, required), discard_changes (boolean, needed for remove with changes). Refused from a subagent with a cwd override.	Main session and subagents. Kept in background subagents.	❌	❌	✅	Tools Reference, Create Custom Subagents
✅ 🧪	EnterPlanMode	Switches to plan mode.	No parameters. Gate: j3.isEnabled(). Main session only (validation error for an agent). Removed from subagents.	Main session.	✅	❌	✅	Tools Reference, Create Custom Subagents
✅ 🧪	ExitPlanMode	Presents the plan and leaves plan mode.	allowedPrompts (deprecated, unused). Gate: complex isEnabled. Kept in a subagent only when its permissionMode is plan.	Main session.	❌	❌	✅	Tools Reference, Configure Permissions
✅	AskUserQuestion	Asks the user 1 to 4 multiple-choice questions.	Removed from every subagent.	Main session.	✅	❌	❌	Tools Reference, Configure Permissions
🔍 🧪	ProposeGoal	Proposes a goal condition for user approval.	condition (string, required), ask_user (boolean, default true). A hidden server-side flag turns it on.	Main session.	✅	❌	✅	Bundle searchHint:"propose a session goal condition for the user to approve with one keypress"
✅	ReportFindings	Reports code-review findings as a list.	level (low, medium, high, xhigh, max, optional), findings (array of at most 32, required). Used only when review instructions ask for it.	Main session.	✅	✅	❌	Tools Reference

Agent Parameters

Parameter	What It Does	Required
description	A short (3-5 word) description of the task.	✅
prompt	The task for the agent.	✅
subagent_type	Type of agent to use.	❌
model	sonnet, opus, haiku, or fable. Overrides the agent definition.	❌
effort	Reasoning effort for this agent. Omitted in some sessions.	❌
run_in_background	Agents run in the background by default. false waits for the result.	❌
name	Name that makes the agent addressable by SendMessage while it runs.	❌
isolation	worktree for a temporary git worktree, or remote for a cloud environment.	❌
cwd	Absolute path to run in. Not with isolation: "worktree". Offered only in some sessions.	❌
team_name	Deprecated and ignored.	❌
mode	Deprecated and ignored.	❌

The source is the Agent input schema in the bundle.

Notes

• Agent was Task before 2.1.63. Task(...) still works as an alias in rules and agent files (Subagents). The bundle alias list holds Task.
• effort on Agent also takes lower and higher when CLAUDE_CODE_SNAPPY_PELICAN is on (or a hidden server-side flag is on) and no model override is set. These are ignored for forks, remote isolation, and teammates (bundle parameter text).

See Also

• Subagents covers custom agents.
• Tools Reference is the docs page.