Extending the plugin

The plugin is designed to be extended. You can add new commands, agents, and templates without modifying the core skill.

Plugin structure

.claude-plugin/plugin.json   -- plugin manifest (name, version, metadata)
commands/                    -- slash command definitions
scripts/                     -- standalone execution scripts
scripts/lib/                 -- shared bash libraries (worktree, checkpoint, deps)
skills/spec-workflow/        -- main skill and reference docs
skills/spec-workflow/references/  -- supplementary reference documents
agents/                      -- subagent definitions
templates/                   -- document scaffolding

Adding a command

Create a new .md file in commands/ with YAML frontmatter:

---
name: spec-mycommand
description: Short description shown in command picker
argument-hint: "[optional-argument]"
allowed-tools:
  - Read
  - Write
  - Bash
  - Task
---

# /spec-mycommand Command

Command body — this is what Claude reads when the command is invoked.

The name field must match the filename (without .md). The allowed-tools list controls which Claude Code tools the command can use.

After adding a command file, restart Claude Code for it to appear.

Adding an agent

Create a new .md file in agents/ with YAML frontmatter:

---
name: spec-myagent
model: sonnet
description: What this agent does
allowed-tools:
  - Read
  - Write
---

# Agent system prompt

The agent's instructions go here.

Agents are spawned by commands via the Task tool. Reference the agent by its fully qualified name: spec-driven:spec-myagent.

Model options: standard (default for most agents), reasoning (for deep reasoning tasks like planning and review).

Adding reference material

Place supplementary documentation in skills/spec-workflow/references/. The main skill file (SKILL.md) references these by relative path. Reference files are loaded by agents when they need detailed guidance on a specific topic.

Existing reference files: - ears-notation.md — EARS pattern reference with examples - design-patterns.md — architecture documentation patterns - task-breakdown.md — task decomposition strategies

Template variables

Templates use {{PLACEHOLDER}} markers that the spec-planner replaces during spec creation. Common placeholders:

Placeholder	Description
{{FEATURE_NAME}}	The feature name passed to /spec

The spec-planner handles substitution — users do not interact with placeholders directly.

Modifying reference documents

Reference documents in skills/spec-workflow/references/ are loaded on demand by agents. You can add new sections, examples, or patterns to any reference file. Changes take effect immediately without restarting Claude Code.

If you add a new reference file, update SKILL.md to reference it in the "Additional Resources" section so agents know it exists.