Skills - AgentFront

Skills are modular knowledge packages that teach AI how to perform multi-step tasks using tools. Unlike tools (which are individual actions), skills are recipes/playbooks that combine tools into coherent workflows.

Skills extend the MCP model by providing workflow guidance. They’re discovered via searchSkills and loaded via loadSkill tools that FrontMCP automatically registers.

Why Skills?

In the Model Context Protocol ecosystem, skills serve a distinct purpose from tools, resources, and prompts:

Aspect	Skill	Tool	Resource	Prompt
Purpose	Multi-step workflows	Execute actions	Provide data	Provide templated instructions
Contains	Instructions + tool references	Execution logic	Read-only data	Message templates
Direction	Model loads on demand	Model triggers execution	Model pulls data	Model uses messages
Side effects	No (guidance only)	Yes (mutations, API calls)	No (read-only)	No (message generation)
Use case	Complex procedures, workflows	Actions, integrations	Context loading	Conversation templates

Skills are ideal for:

Complex workflows — multi-step procedures like PR reviews, deployments, migrations
Domain expertise — codified knowledge from experts (security audits, code reviews)
Orchestration guides — coordinating multiple tools in sequence
Reusable playbooks — standardized procedures across teams

How Skills Work

Creating Skills

Class Style

Use class decorators for skills that need dependency injection or lifecycle hooks:

import { Skill, SkillContext } from '@frontmcp/sdk';

@Skill({
  name: 'review-pr',
  description: 'Review a GitHub pull request for code quality and issues',
  instructions: `
    ## PR Review Process

    1. First, fetch the PR details using github_get_pr
    2. Review the changed files using github_get_pr_files
    3. For each file, analyze for:
       - Code quality issues
       - Security vulnerabilities
       - Performance concerns
    4. Add review comments using github_add_review_comment
    5. Submit the review using github_submit_review
  `,
  tools: [
    { name: 'github_get_pr', purpose: 'Fetch PR details', required: true },
    { name: 'github_get_pr_files', purpose: 'Get changed files' },
    { name: 'github_add_review_comment', purpose: 'Add inline comments' },
    { name: 'github_submit_review', purpose: 'Submit final review' },
  ],
  tags: ['github', 'code-review', 'quality'],
})
class ReviewPRSkill extends SkillContext {}

Function Style

For simpler skills, use the functional builder:

import { skill } from '@frontmcp/sdk';

const DeployAppSkill = skill({
  name: 'deploy-app',
  description: 'Deploy application to production environment',
  instructions: { file: './skills/deploy-app.md' },
  tools: ['docker_build', 'docker_push', 'k8s_apply'],
  tags: ['deployment', 'devops'],
});

Registering Skills

Add skills to your app via the skills array:

import { App } from '@frontmcp/sdk';

@App({
  id: 'my-app',
  name: 'My Application',
  tools: [GitHubTool, DockerTool, K8sTool],
  skills: [ReviewPRSkill, DeployAppSkill, RefactorSkill],
})
class MyApp {}

Skills are automatically:

Indexed for search via searchSkills
Loadable via loadSkill with tool availability info

Skill Metadata

@Skill({
  name: string,              // Required: kebab-case, max 64 chars
  description: string,       // Required: max 1024 chars, no XML tags
  instructions: InstructionSource, // Required: detailed guidance (see below)
  tools?: ToolRef[],         // Optional: tool references with purpose
  tags?: string[],           // Optional: categorization tags
  parameters?: Parameter[],  // Optional: input parameters
  examples?: Example[],      // Optional: usage examples
  priority?: number,         // Optional: search ranking weight (default: 0)
  hideFromDiscovery?: boolean, // Optional: hide from searchSkills (default: false)
  visibility?: 'mcp' | 'http' | 'both', // Optional: discovery visibility (default: 'both')
  toolValidation?: 'strict' | 'warn' | 'ignore', // Optional: tool ref validation (default: 'warn')
  license?: string,          // Optional: license name (e.g. 'MIT')
  compatibility?: string,    // Optional: environment requirements (max 500 chars)
  specMetadata?: Record<string, string>, // Optional: arbitrary key-value metadata
  allowedTools?: string,     // Optional: space-delimited pre-approved tools
  resources?: SkillResources, // Optional: bundled resource directories
})

Field descriptions:

Field	Description
`name`	Unique identifier, must be kebab-case (max 64 chars, no consecutive hyphens)
`description`	Short text for discovery (max 1024 chars, no XML/HTML tags)
`instructions`	Detailed step-by-step guidance (inline, file, or URL)
`tools`	Tools this skill uses, with optional purpose descriptions
`tags`	Categorization for filtering and organization
`parameters`	Input values that customize skill behavior
`examples`	Scenarios demonstrating when and how to use the skill
`priority`	Higher values appear earlier in search results
`hideFromDiscovery`	When `true`, skill is loadable but not listed in search
`visibility`	Where this skill is discoverable: `mcp`, `http`, or `both`
`toolValidation`	How to handle missing tool references: `strict`, `warn`, `ignore`
`license`	License name or reference (per Agent Skills spec)
`compatibility`	Environment requirements (max 500 chars, per Agent Skills spec)
`specMetadata`	Arbitrary key-value metadata (maps to spec `metadata` field)
`allowedTools`	Space-delimited pre-approved tools (maps to spec `allowed-tools`)
`resources`	Bundled resource directories (`scripts/`, `references/`, `assets/`)

Name Validation

Skill names follow strict kebab-case rules per the Anthropic Agent Skills specification:

Lowercase letters, numbers, and hyphens only
Must start and end with a letter or number
No consecutive hyphens (--)
Maximum 64 characters

// Valid names
'review-pr'           // ✓
'deploy-v2'           // ✓
'a'                   // ✓

// Invalid names
'Review-PR'           // ✗ uppercase
'review_pr'           // ✗ underscore
'review--pr'          // ✗ consecutive hyphens
'-review-pr'          // ✗ starts with hyphen

Description Validation

Maximum 1024 characters
Must not contain XML/HTML tags (per Agent Skills spec)

Instruction Sources

Skills support three instruction sources:

Inline String (Recommended)

Best for dependency tracking and version control:

@Skill({
  name: 'security-audit',
  instructions: `
    ## Security Audit Process

    1. Scan dependencies with security_scan_deps
    2. Check for hardcoded secrets with secrets_scan
    3. Analyze code for OWASP top 10 with code_analyze
    4. Generate report with create_report
  `,
})

File Path

Load from a markdown file at runtime:

@Skill({
  name: 'migration-guide',
  instructions: { file: './skills/database-migration.md' },
})

URL

Fetch from a remote source at load time:

@Skill({
  name: 'external-workflow',
  instructions: { url: 'https://docs.example.com/workflows/deploy.md' },
})

Inline instructions are recommended because they enable static analysis, type checking, and ensure the skill definition is complete and self-contained.

Tool References

Reference tools with simple names or detailed objects:

Simple References

@Skill({
  name: 'simple-workflow',
  tools: ['github_create_pr', 'github_merge_pr', 'slack_notify'],
})

Detailed References

Include purpose and required flag for better LLM understanding:

@Skill({
  name: 'detailed-workflow',
  tools: [
    { name: 'github_create_pr', purpose: 'Create the pull request', required: true },
    { name: 'github_request_review', purpose: 'Request code review' },
    { name: 'github_merge_pr', purpose: 'Merge after approval', required: true },
    { name: 'slack_notify', purpose: 'Notify team of completion' },
  ],
})

Property	Description
`name`	The tool’s identifier
`purpose`	Explains why/how the tool is used in this skill
`required`	If `true`, skill may not work without this tool

Parameters

Define input parameters that customize skill behavior:

@Skill({
  name: 'review-pr',
  parameters: [
    {
      name: 'pr_url',
      description: 'URL of the pull request to review',
      required: true,
      type: 'string',
    },
    {
      name: 'focus_areas',
      description: 'Specific areas to focus on (security, performance, etc.)',
      type: 'array',
    },
    {
      name: 'strictness',
      description: 'Review strictness level',
      type: 'string',
      default: 'normal',
    },
  ],
})

Property	Description
`name`	Parameter identifier
`description`	Human-readable description
`required`	Whether the parameter must be provided
`type`	Type hint: `string`, `number`, `boolean`, `object`, `array`
`default`	Default value if not provided

Examples

Provide usage examples to help LLMs understand when to use the skill:

@Skill({
  name: 'review-pr',
  examples: [
    {
      scenario: 'User asks to review a PR for security issues',
      parameters: {
        pr_url: 'https://github.com/org/repo/pull/123',
        focus_areas: ['security', 'authentication'],
      },
      expectedOutcome: 'Detailed security-focused review with inline comments',
    },
    {
      scenario: 'User wants a quick review of a small PR',
      parameters: {
        pr_url: 'https://github.com/org/repo/pull/456',
        strictness: 'lenient',
      },
      expectedOutcome: 'High-level review focusing on major issues only',
    },
  ],
})

Real-World Examples

PR Review Skill

@Skill({
  name: 'review-pr',
  description: 'Review a GitHub pull request for code quality, security, and best practices',
  instructions: `
    ## PR Review Workflow

    ### Phase 1: Gather Context
    1. Use github_get_pr to fetch PR metadata (title, description, author)
    2. Use github_get_pr_files to get the list of changed files
    3. For large PRs, prioritize: security-sensitive files, API changes, database migrations

    ### Phase 2: Analyze Changes
    For each changed file:
    - Check for security vulnerabilities (SQL injection, XSS, auth bypass)
    - Review error handling and edge cases
    - Verify test coverage for new functionality
    - Look for performance issues (N+1 queries, memory leaks)

    ### Phase 3: Provide Feedback
    1. Use github_add_review_comment for inline suggestions
    2. Group related issues together
    3. Distinguish between blocking issues and suggestions

    ### Phase 4: Submit Review
    Use github_submit_review with:
    - APPROVE: No blocking issues found
    - REQUEST_CHANGES: Blocking issues that must be fixed
    - COMMENT: Suggestions only, no blocking issues
  `,
  tools: [
    { name: 'github_get_pr', purpose: 'Fetch PR metadata and description', required: true },
    { name: 'github_get_pr_files', purpose: 'List all changed files', required: true },
    { name: 'github_add_review_comment', purpose: 'Add inline review comments' },
    { name: 'github_submit_review', purpose: 'Submit the final review verdict' },
  ],
  tags: ['github', 'code-review', 'quality', 'security'],
  parameters: [
    { name: 'pr_url', description: 'Pull request URL', required: true },
    { name: 'focus_areas', description: 'Areas to focus on', type: 'array' },
  ],
})
class ReviewPRSkill extends SkillContext {}

Deploy Application Skill

@Skill({
  name: 'deploy-app',
  description: 'Deploy application to Kubernetes production environment',
  instructions: `
    ## Deployment Workflow

    ### Pre-flight Checks
    1. Verify all tests pass with run_tests
    2. Check for security vulnerabilities with security_scan
    3. Ensure environment variables are configured

    ### Build Phase
    1. Build Docker image with docker_build
    2. Tag with version and commit SHA
    3. Push to registry with docker_push

    ### Deploy Phase
    1. Update Kubernetes manifests with k8s_update_manifests
    2. Apply changes with k8s_apply
    3. Wait for rollout with k8s_wait_rollout

    ### Post-deployment
    1. Run smoke tests with run_smoke_tests
    2. Notify team with slack_notify
    3. If any step fails, trigger k8s_rollback
  `,
  tools: [
    { name: 'run_tests', purpose: 'Run test suite', required: true },
    { name: 'security_scan', purpose: 'Scan for vulnerabilities' },
    { name: 'docker_build', purpose: 'Build container image', required: true },
    { name: 'docker_push', purpose: 'Push to container registry', required: true },
    { name: 'k8s_apply', purpose: 'Apply Kubernetes manifests', required: true },
    { name: 'k8s_wait_rollout', purpose: 'Wait for deployment completion' },
    { name: 'k8s_rollback', purpose: 'Rollback on failure' },
    { name: 'slack_notify', purpose: 'Send deployment notifications' },
  ],
  tags: ['deployment', 'kubernetes', 'devops', 'production'],
})
class DeployAppSkill extends SkillContext {}

Code Refactoring Skill

const RefactorSkill = skill({
  name: 'refactor-code',
  description: 'Safely refactor code with comprehensive testing',
  instructions: `
    ## Refactoring Workflow

    ### Analysis
    1. Read the target code with read_file
    2. Identify code smells and improvement opportunities
    3. Plan refactoring steps (small, testable changes)

    ### Refactoring Loop
    For each planned change:
    1. Make the change with edit_file
    2. Run tests with run_tests
    3. If tests fail, revert and try alternative approach
    4. Commit working changes with git_commit

    ### Verification
    1. Run full test suite
    2. Check for regressions
    3. Review final diff with git_diff
  `,
  tools: [
    { name: 'read_file', purpose: 'Read source code', required: true },
    { name: 'edit_file', purpose: 'Make code changes', required: true },
    { name: 'run_tests', purpose: 'Verify changes', required: true },
    { name: 'git_commit', purpose: 'Commit working changes' },
    { name: 'git_diff', purpose: 'Review final changes' },
  ],
  tags: ['refactoring', 'code-quality', 'testing'],
});

MCP Protocol Integration

FrontMCP automatically registers two flows for skill discovery and loading:

Flow	Description
`skills/search`	Search for relevant skills by query, tags, or required tools
`skills/load`	Load a skill’s full content including instructions and tool info

searchSkills

Search for skills matching a query:

{
  "method": "skills/search",
  "params": {
    "query": "review pull request",
    "tags": ["github"],
    "limit": 10,
    "requireAllTools": false
  }
}

Response:

{
  "skills": [
    {
      "id": "review-pr",
      "name": "review-pr",
      "description": "Review a GitHub pull request...",
      "score": 0.95,
      "tags": ["github", "code-review"],
      "tools": [
        { "name": "github_get_pr", "available": true },
        { "name": "github_submit_review", "available": true }
      ],
      "source": "local"
    }
  ],
  "total": 5,
  "hasMore": false
}

loadSkill

Load a skill’s full content:

{
  "method": "skills/load",
  "params": {
    "skillId": "review-pr",
    "format": "full"
  }
}

Response:

{
  "skill": {
    "id": "review-pr",
    "name": "review-pr",
    "description": "Review a GitHub pull request...",
    "instructions": "## PR Review Workflow\n\n### Phase 1...",
    "tools": [
      { "name": "github_get_pr", "purpose": "Fetch PR metadata", "available": true },
      { "name": "github_submit_review", "purpose": "Submit review", "available": true }
    ],
    "parameters": [
      { "name": "pr_url", "required": true }
    ]
  },
  "availableTools": ["github_get_pr", "github_submit_review"],
  "missingTools": [],
  "isComplete": true,
  "formattedContent": "# Skill: review-pr\n\n## Instructions\n..."
}

Tool Validation

When loading a skill, FrontMCP validates tool availability:

Available tools: Tools registered in the current scope
Missing tools: Referenced tools that don’t exist
Hidden tools: Tools that exist but are hidden from discovery

Handling Missing Tools

Skills are still loadable even when some tools are missing:

{
  "skill": { ... },
  "availableTools": ["github_get_pr"],
  "missingTools": ["github_submit_review"],
  "isComplete": false,
  "warning": "Skill 'review-pr' is missing 1 tool(s): github_submit_review. Some functionality may not work."
}

The LLM receives this information and can:

Proceed with available tools only
Inform the user about limitations
Suggest alternative approaches

Setting required: true on a tool reference indicates the skill cannot function without it. Missing required tools are highlighted in the warning message.

Search Algorithm

Skills are searched using TF-IDF with weighted terms:

Field	Weight
description	3x
tags	2x
tools	1x
name	1x

Results are ranked by:

Relevance score
Priority field (higher = earlier)
Tool availability (complete skills rank higher)

Agent Skills Specification Alignment

FrontMCP skills are aligned with the Anthropic Agent Skills specification. This means you can use standard SKILL.md files and skill directories with FrontMCP.

New Spec Fields

Fields from the Agent Skills spec are available as first-class properties:

@Skill({
  name: 'deploy-app',
  description: 'Deploy application to production',
  instructions: '...',
  tools: ['docker_build', 'k8s_apply'],

  // Agent Skills spec fields
  license: 'MIT',
  compatibility: 'Requires Docker 24+ and kubectl',
  specMetadata: {
    author: 'platform-team',
    version: '2.1.0',
    category: 'devops',
  },
  allowedTools: 'Read Edit Bash(docker build) Bash(kubectl apply)',
  resources: {
    scripts: './skills/deploy-app/scripts',
    references: './skills/deploy-app/references',
  },
})
class DeployAppSkill extends SkillContext {}

SKILL.md Frontmatter

FrontMCP can parse SKILL.md files with YAML frontmatter, the standard format from the Agent Skills specification:

---
name: review-pr
description: Review a GitHub pull request
license: MIT
compatibility: Requires git CLI
tags:
  - github
  - code-review
metadata:
  author: dev-team
  version: "1.0"
allowed-tools: Read Edit Bash(git diff)
---
# PR Review Instructions

1. Fetch the PR details
2. Review each changed file
3. Add review comments
4. Submit the review

The frontmatter fields are mapped to FrontMCP metadata:

metadata → specMetadata
allowed-tools → allowedTools
All other fields map directly

The markdown body becomes the instructions content.

When loading instructions from a file, FrontMCP automatically strips YAML frontmatter so you get clean instruction content.

Loading Skill Directories

Load complete skill directories following the Agent Skills spec structure:

skills/
  review-pr/
    SKILL.md           # Required: frontmatter + instructions
    scripts/           # Optional: automation scripts
    references/        # Optional: reference documents
    assets/            # Optional: images, diagrams, etc.

Using `skillDir()`

import { skillDir } from '@frontmcp/sdk';

// Load a skill directory
const reviewSkill = await skillDir('./skills/review-pr');

@App({
  name: 'my-app',
  skills: [reviewSkill],
})
class MyApp {}

Using `loadSkillDirectory()`

For more control:

import { loadSkillDirectory, scanSkillResources } from '@frontmcp/sdk';

// Load with full metadata
const record = await loadSkillDirectory('./skills/review-pr');
// record.kind === 'FILE'
// record.metadata contains parsed frontmatter
// record.metadata.resources contains detected directories

// Or just scan for resource directories
const { resources, hasSkillMd } = await scanSkillResources('./skills/review-pr');

Allowed Tools

The allowedTools field lists tools that are pre-approved for the skill. This is useful for skill sessions where tool access is restricted:

@Skill({
  name: 'code-review',
  description: 'Review code changes',
  instructions: '...',
  tools: ['github_get_pr', 'github_add_comment'],
  allowedTools: 'Read Edit Bash(git diff) Bash(git log)',
})

Tools in allowedTools don’t require additional user confirmation during skill sessions.

Best Practices

Do:

Write clear, step-by-step instructions that guide the LLM through the workflow
Reference specific tools with purpose descriptions
Include examples for common scenarios
Use tags for categorization and discovery
Keep skills focused on a single workflow or domain

Don’t:

Create overly broad skills that try to do everything
Skip tool purposes (hurts discoverability and understanding)
Hardcode values that should be parameters
Forget to list required tools
Create skills for simple, single-tool operations (just use the tool directly)

​Why Skills?

​How Skills Work

​Creating Skills

​Class Style

​Function Style

​Registering Skills

​Skill Metadata

​Name Validation

​Description Validation

​Instruction Sources

​Inline String (Recommended)

​File Path

​URL

​Tool References

​Simple References

​Detailed References

​Parameters

​Examples

​Real-World Examples

​PR Review Skill

​Deploy Application Skill

​Code Refactoring Skill

​MCP Protocol Integration

​searchSkills

​loadSkill

​Tool Validation

​Handling Missing Tools

​Search Algorithm

​Agent Skills Specification Alignment

​New Spec Fields

​SKILL.md Frontmatter

​Loading Skill Directories

​Using skillDir()

​Using loadSkillDirectory()

​Allowed Tools

​Best Practices

Why Skills?

How Skills Work

Creating Skills

Class Style

Function Style

Registering Skills

Skill Metadata

Name Validation

Description Validation

Instruction Sources

Inline String (Recommended)

File Path

URL

Tool References

Simple References

Detailed References

Parameters

Examples

Real-World Examples

PR Review Skill

Deploy Application Skill

Code Refactoring Skill

MCP Protocol Integration

searchSkills

loadSkill

Tool Validation

Handling Missing Tools

Search Algorithm

Agent Skills Specification Alignment

New Spec Fields

SKILL.md Frontmatter

Loading Skill Directories

Using `skillDir()`

Using `loadSkillDirectory()`

Allowed Tools

Best Practices