github-spec-kit/extensions/EXTENSION-API-REFERENCE.md

Extension API Reference

Technical reference for Spec Kit extension system APIs and manifest schema.

Table of Contents

1. Extension Manifest
2. Python API
3. Command File Format
4. Configuration Schema
5. Hook System
6. CLI Commands

---

Extension Manifest

Schema Version 1.0

File: extension.yml

schema_version: "1.0"  # Required

extension:
  id: string           # Required, pattern: ^[a-z0-9-]+$
  name: string         # Required, human-readable name
  version: string      # Required, semantic version (X.Y.Z)
  description: string  # Required, brief description (<200 chars)
  author: string       # Required
  repository: string   # Required, valid URL
  license: string      # Required (e.g., "MIT", "Apache-2.0")
  homepage: string     # Optional, valid URL

requires:
  speckit_version: string  # Required, version specifier (>=X.Y.Z)
  tools:                   # Optional, array of tool requirements
    - name: string         # Tool name
      version: string      # Optional, version specifier
      required: boolean    # Optional, default: false

provides:
  commands:              # Required, at least one command
    - name: string       # Required, pattern: ^speckit\.[a-z0-9-]+\.[a-z0-9-]+$
      file: string       # Required, relative path to command file
      description: string # Required
      aliases: [string]  # Optional, same pattern as name; namespace must match extension.id and must not shadow core or installed extension commands

  config:                # Optional, array of config files
    - name: string       # Config file name
      template: string   # Template file path
      description: string
      required: boolean  # Default: false

hooks:                   # Optional, event hooks. Each event accepts either form below.
  event_name:            # e.g., "after_specify", "after_plan", "after_tasks", "after_implement"
    command: string      # Command to execute
    priority: integer    # Optional, >= 1, default 10 (lower runs first)
    optional: boolean    # Default: true
    prompt: string       # Prompt text for optional hooks
    description: string  # Hook description
    condition: string    # Optional, condition expression
  another_event:         # Any event may instead use a list of mappings (multiple commands)
    - command: string    # Same fields as the single mapping, per entry
      priority: integer
    - command: string
      priority: integer

tags:                    # Optional, array of tags (2-10 recommended)
  - string

defaults:                # Optional, default configuration values
  key: value             # Any YAML structure

Field Specifications

extension.id

• Type: string
• Pattern: ^[a-z0-9-]+$
• Description: Unique extension identifier
• Examples: jira, linear, azure-devops
• Invalid: Jira, my_extension, extension.id

extension.version

• Type: string
• Format: Semantic versioning (X.Y.Z)
• Description: Extension version
• Examples: 1.0.0, 0.9.5, 2.1.3
• Invalid: v1.0, 1.0, 1.0.0-beta

requires.speckit_version

• Type: string
• Format: Version specifier
• Description: Required spec-kit version range
• Examples:
  • >=0.1.0 - Any version 0.1.0 or higher
  • >=0.1.0,<2.0.0 - Version 0.1.x or 1.x
  • ==0.1.0 - Exactly 0.1.0
• Invalid: 0.1.0, >= 0.1.0 (space), latest

provides.commands[].name

• Type: string
• Pattern: ^speckit\.[a-z0-9-]+\.[a-z0-9-]+$
• Description: Namespaced command name
• Format: speckit.{extension-id}.{command-name}
• Examples: speckit.jira.specstoissues, speckit.linear.sync
• Invalid: jira.specstoissues, speckit.command, speckit.jira.CreateIssues

hooks

• Type: object
• Keys: Event names (e.g., after_specify, after_plan, after_tasks, after_implement, before_analyze)
• Value: A single hook mapping, or a list of hook mappings to register multiple commands on one event
• Description: Hooks that execute at lifecycle events
• Events: Defined by core spec-kit commands
• Ordering: Within an event, hooks run by ascending priority (integer ≥ 1, default 10; lower runs first; equal priorities keep authoring order via a stable sort)

---

Python API

ExtensionManifest

Module: specify_cli.extensions

from specify_cli.extensions import ExtensionManifest

manifest = ExtensionManifest(Path("extension.yml"))

Properties:

manifest.id                        # str: Extension ID
manifest.name                      # str: Extension name
manifest.version                   # str: Version
manifest.description               # str: Description
manifest.requires_speckit_version  # str: Required spec-kit version
manifest.commands                  # List[Dict]: Command definitions
manifest.hooks                     # Dict: Hook definitions

Methods:

manifest.get_hash()  # str: SHA256 hash of manifest file

Exceptions:

ValidationError       # Invalid manifest structure
CompatibilityError    # Incompatible with current spec-kit version

ExtensionRegistry

Module: specify_cli.extensions

from specify_cli.extensions import ExtensionRegistry

registry = ExtensionRegistry(extensions_dir)

Methods:

# Add extension to registry
registry.add(extension_id: str, metadata: dict)

# Remove extension from registry
registry.remove(extension_id: str)

# Get extension metadata
metadata = registry.get(extension_id: str)  # Optional[dict]

# List all extensions
extensions = registry.list()  # Dict[str, dict]

# Check if installed
is_installed = registry.is_installed(extension_id: str)  # bool

Registry Format:

{
  "schema_version": "1.0",
  "extensions": {
    "jira": {
      "version": "1.0.0",
      "source": "catalog",
      "manifest_hash": "sha256...",
      "enabled": true,
      "registered_commands": ["speckit.jira.specstoissues", ...],
      "installed_at": "2026-01-28T..."
    }
  }
}

ExtensionManager

Module: specify_cli.extensions

from specify_cli.extensions import ExtensionManager

manager = ExtensionManager(project_root)

Methods:

# Install from directory
manifest = manager.install_from_directory(
    source_dir: Path,
    speckit_version: str,
    register_commands: bool = True
)  # Returns: ExtensionManifest

# Install from ZIP
manifest = manager.install_from_zip(
    zip_path: Path,
    speckit_version: str
)  # Returns: ExtensionManifest

# Remove extension
success = manager.remove(
    extension_id: str,
    keep_config: bool = False
)  # Returns: bool

# List installed extensions
extensions = manager.list_installed()  # List[Dict]

# Get extension manifest
manifest = manager.get_extension(extension_id: str)  # Optional[ExtensionManifest]

# Check compatibility
manager.check_compatibility(
    manifest: ExtensionManifest,
    speckit_version: str
)  # Raises: CompatibilityError if incompatible

CatalogEntry

Module: specify_cli.extensions

Represents a single catalog in the active catalog stack.

from specify_cli.extensions import CatalogEntry

entry = CatalogEntry(
    url="https://example.com/catalog.json",
    name="default",
    priority=1,
    install_allowed=True,
    description="Built-in catalog of installable extensions",
)

Fields:

Field	Type	Description
url	str	Catalog URL (must use HTTPS, or HTTP for localhost)
name	str	Human-readable catalog name
priority	int	Sort order (lower = higher priority, wins on conflicts)
install_allowed	bool	Whether extensions from this catalog can be installed
description	str	Optional human-readable description of the catalog (default: empty)

ExtensionCatalog

Module: specify_cli.extensions

from specify_cli.extensions import ExtensionCatalog

catalog = ExtensionCatalog(project_root)

Class attributes:

ExtensionCatalog.DEFAULT_CATALOG_URL    # default catalog URL
ExtensionCatalog.COMMUNITY_CATALOG_URL  # community catalog URL

Methods:

# Get the ordered list of active catalogs
entries = catalog.get_active_catalogs()  # List[CatalogEntry]

# Fetch catalog (primary catalog, backward compat)
catalog_data = catalog.fetch_catalog(force_refresh: bool = False)  # Dict

# Search extensions across all active catalogs
# Each result includes _catalog_name and _install_allowed
results = catalog.search(
    query: Optional[str] = None,
    tag: Optional[str] = None,
    author: Optional[str] = None,
    verified_only: bool = False
)  # Returns: List[Dict]  — each dict includes _catalog_name, _install_allowed

# Get extension info (searches all active catalogs)
# Returns None if not found; includes _catalog_name and _install_allowed
ext_info = catalog.get_extension_info(extension_id: str)  # Optional[Dict]

# Check cache validity (primary catalog)
is_valid = catalog.is_cache_valid()  # bool

# Clear all catalog caches
catalog.clear_cache()

Result annotation fields:

Each extension dict returned by search() and get_extension_info() includes:

Field	Type	Description
_catalog_name	str	Name of the source catalog
_install_allowed	bool	Whether installation is allowed from this catalog

Catalog config file (.specify/extension-catalogs.yml):

catalogs:
  - name: "default"
    url: "https://raw.githubusercontent.com/github/spec-kit/main/extensions/catalog.json"
    priority: 1
    install_allowed: true
    description: "Built-in catalog of installable extensions"
  - name: "community"
    url: "https://raw.githubusercontent.com/github/spec-kit/main/extensions/catalog.community.json"
    priority: 2
    install_allowed: false
    description: "Community-contributed extensions (discovery only)"

HookExecutor

Module: specify_cli.extensions

from specify_cli.extensions import HookExecutor

hook_executor = HookExecutor(project_root)

Methods:

# Get project config
config = hook_executor.get_project_config()  # Dict

# Save project config
hook_executor.save_project_config(config: Dict)

# Register hooks
hook_executor.register_hooks(manifest: ExtensionManifest)

# Unregister hooks
hook_executor.unregister_hooks(extension_id: str)

# Get hooks for event
hooks = hook_executor.get_hooks_for_event(event_name: str)  # List[Dict]

# Check if hook should execute
should_run = hook_executor.should_execute_hook(hook: Dict)  # bool

# Format hook message
message = hook_executor.format_hook_message(
    event_name: str,
    hooks: List[Dict]
)  # str

CommandRegistrar

Module: specify_cli.extensions

from specify_cli.extensions import CommandRegistrar

registrar = CommandRegistrar()

Methods:

# Register commands for Claude Code
registered = registrar.register_commands_for_claude(
    manifest: ExtensionManifest,
    extension_dir: Path,
    project_root: Path
)  # Returns: List[str] (command names)

# Parse frontmatter
frontmatter, body = registrar.parse_frontmatter(content: str)

# Render frontmatter
yaml_text = registrar.render_frontmatter(frontmatter: Dict)  # str

---

Command File Format

Universal Command Format

File: commands/{command-name}.md

---
description: "Command description"
tools:
  - 'mcp-server/tool_name'
  - 'other-mcp-server/other_tool'
---

# Command Title

Command documentation in Markdown.

## Prerequisites

1. Requirement 1
2. Requirement 2

## User Input

$ARGUMENTS

## Steps

### Step 1: Description

Instruction text...

\`\`\`bash
# Shell commands
\`\`\`

### Step 2: Another Step

More instructions...

## Configuration Reference

Information about configuration options.

## Notes

Additional notes and tips.

Frontmatter Fields

description: string   # Required, brief command description
tools: [string]       # Optional, MCP tools required

Special Variables

• $ARGUMENTS - Placeholder for user-provided arguments

• Extension context automatically injected:

  <!-- Extension: {extension-id} -->
  <!-- Config: .specify/extensions/{extension-id}/ -->
  

---

Configuration Schema

Extension Config File

File: .specify/extensions/{extension-id}/{extension-id}-config.yml

Extensions define their own config schema. Common patterns:

# Connection settings
connection:
  url: string
  api_key: string

# Project settings
project:
  key: string
  workspace: string

# Feature flags
features:
  enabled: boolean
  auto_sync: boolean

# Defaults
defaults:
  labels: [string]
  assignee: string

# Custom fields
field_mappings:
  internal_name: "external_field_id"

Config Layers

1. Extension Defaults (from extension.yml defaults section)
2. Project Config ({extension-id}-config.yml)
3. Local Override ({extension-id}-config.local.yml, gitignored)
4. Environment Variables (SPECKIT_{EXTENSION}_*)

Environment Variable Pattern

Format: SPECKIT_{EXTENSION}_{KEY}

Examples:

• SPECKIT_JIRA_PROJECT_KEY
• SPECKIT_LINEAR_API_KEY
• SPECKIT_GITHUB_TOKEN

---

Hook System

Hook Definition

Each event accepts either a single hook mapping or a list of mappings. A list registers multiple commands on the same event.

Single mapping (in extension.yml):

hooks:
  after_tasks:
    command: "speckit.jira.specstoissues"
    optional: true
    prompt: "Create Jira issues from tasks?"
    description: "Automatically create Jira hierarchy"
    condition: null

List of mappings with priority:

hooks:
  after_plan:
    - command: "speckit.my-ext.verify"
      priority: 5
      optional: false
      description: "Verify the plan"
    - command: "speckit.my-ext.report"
      priority: 10
      optional: true
      prompt: "Generate the report?"
      description: "Generate a report from the plan"

Within a single manifest list, a repeated command is deduped as "last wins" and moved to the end, so it also breaks equal-priority ties in authoring order.

Hook Events

Standard events (defined by core):

• before_specify - Before specification generation
• after_specify - After specification generation
• before_plan - Before implementation planning
• after_plan - After implementation planning
• before_tasks - Before task generation
• after_tasks - After task generation
• before_implement - Before implementation
• after_implement - After implementation
• before_analyze - Before cross-artifact analysis
• after_analyze - After cross-artifact analysis
• before_checklist - Before checklist generation
• after_checklist - After checklist generation
• before_clarify - Before spec clarification
• after_clarify - After spec clarification
• before_constitution - Before constitution update
• after_constitution - After constitution update
• before_taskstoissues - Before tasks-to-issues conversion
• after_taskstoissues - After tasks-to-issues conversion

Hook Configuration

In .specify/extensions.yml:

hooks:
  after_tasks:
    - extension: jira
      command: speckit.jira.specstoissues
      enabled: true
      optional: true
      prompt: "Create Jira issues from tasks?"
      description: "..."
      condition: null

Hook Message Format

## Extension Hooks

**Optional Hook**: {extension}
Command: `/{command}`
Description: {description}

Prompt: {prompt}
To execute: `/{command}`

Or for mandatory hooks:

**Automatic Hook**: {extension}
Executing: `/{command}`
EXECUTE_COMMAND: {command}

---

CLI Commands

extension list

Usage: specify extension list [OPTIONS]

Options:

• --available - Show available extensions from catalog
• --all - Show both installed and available

Output: List of installed extensions with metadata

extension catalog list

Usage: specify extension catalog list

Lists all active catalogs in the current catalog stack, showing name, description, URL, priority, and install_allowed status.

extension catalog add

Usage: specify extension catalog add URL [OPTIONS]

Options:

• --name NAME - Catalog name (required)
• --priority INT - Priority (lower = higher priority, default: 10)
• --install-allowed / --no-install-allowed - Allow installs from this catalog (default: false)
• --description TEXT - Optional description of the catalog

Arguments:

• URL - Catalog URL (must use HTTPS)

Adds a catalog entry to .specify/extension-catalogs.yml.

extension catalog remove

Usage: specify extension catalog remove NAME

Arguments:

• NAME - Catalog name to remove

Removes a catalog entry from .specify/extension-catalogs.yml.

extension add

Usage: specify extension add EXTENSION [OPTIONS]

Options:

• --from URL - Install from custom URL
• --dev PATH - Install from local directory

Arguments:

• EXTENSION - Extension name or URL

Note: Extensions from catalogs with install_allowed: false cannot be installed via this command.

extension remove

Usage: specify extension remove EXTENSION [OPTIONS]

Options:

• --keep-config - Preserve config files
• --force - Skip confirmation

Arguments:

• EXTENSION - Extension ID

extension search

Usage: specify extension search [QUERY] [OPTIONS]

Searches all active catalogs simultaneously. Results include source catalog name and install_allowed status.

Options:

• --tag TAG - Filter by tag
• --author AUTHOR - Filter by author
• --verified - Show only verified extensions

Arguments:

• QUERY - Optional search query

extension info

Usage: specify extension info EXTENSION

Shows source catalog and install_allowed status.

Arguments:

• EXTENSION - Extension ID

extension update

Usage: specify extension update [EXTENSION]

Arguments:

• EXTENSION - Optional, extension ID (default: all)

extension enable

Usage: specify extension enable EXTENSION

Arguments:

• EXTENSION - Extension ID

extension disable

Usage: specify extension disable EXTENSION

Arguments:

• EXTENSION - Extension ID

---

Exceptions

ValidationError

Raised when extension manifest validation fails.

from specify_cli.extensions import ValidationError

try:
    manifest = ExtensionManifest(path)
except ValidationError as e:
    print(f"Invalid manifest: {e}")

CompatibilityError

Raised when extension is incompatible with current spec-kit version.

from specify_cli.extensions import CompatibilityError

try:
    manager.check_compatibility(manifest, "0.1.0")
except CompatibilityError as e:
    print(f"Incompatible: {e}")

ExtensionError

Base exception for all extension-related errors.

from specify_cli.extensions import ExtensionError

try:
    manager.install_from_directory(path, "0.1.0")
except ExtensionError as e:
    print(f"Extension error: {e}")

---

Version Functions

version_satisfies

Check if a version satisfies a specifier.

from specify_cli.extensions import version_satisfies

# True if 1.2.3 satisfies >=1.0.0,<2.0.0
satisfied = version_satisfies("1.2.3", ">=1.0.0,<2.0.0")  # bool

---

File System Layout

.specify/
├── extensions/
│   ├── .registry               # Extension registry (JSON)
│   ├── .cache/                 # Catalog cache
│   │   ├── catalog.json
│   │   └── catalog-metadata.json
│   ├── .backup/                # Config backups
│   │   └── {ext}-{config}.yml
│   ├── {extension-id}/         # Extension directory
│   │   ├── extension.yml       # Manifest
│   │   ├── {ext}-config.yml    # User config
│   │   ├── {ext}-config.local.yml  # Local overrides (gitignored)
│   │   ├── {ext}-config.template.yml  # Template
│   │   ├── commands/           # Command files
│   │   │   └── *.md
│   │   ├── scripts/            # Helper scripts
│   │   │   └── *.sh
│   │   ├── docs/               # Documentation
│   │   └── README.md
│   └── extensions.yml          # Project extension config
└── scripts/                    # (existing spec-kit)

.claude/
└── commands/
    └── speckit.{ext}.{cmd}.md  # Registered commands

---

Last Updated: 2026-01-28 API Version: 1.0 Spec Kit Version: 0.1.0