Migrating an MCP Tool to Effector

Already have an MCP tool? Add types and composition in 5 minutes.

What You Get

• Type-safe interfaces (input/output/context)
• Static composition checking with other capabilities
• Security audit via effector-audit
• Automatic discovery by type in registries

Step 1: Create effector.toml

Next to your existing MCP tool, create effector.toml:

[effector]
name = "your-tool-name"
version = "0.1.0"
type = "skill"
description = "What your tool does in one line"

[effector.interface]
input = "String"        # or CodeDiff, FilePath, JSON, URL, etc.
output = "Markdown"     # or JSON, ReviewReport, Summary, etc.
context = []            # e.g. ["GitHubCredentials"] if needed

[effector.permissions]
network = false         # true if your tool makes HTTP requests
subprocess = false      # true if your tool spawns processesCopy

Choosing Types

Pick from the 40 standard types in effector-types:

Input types: String, FilePath, URL, JSON, RepositoryRef, CodeDiff, CodeSnippet, IssueRef, PullRequestRef, CommitRef, TextDocument, DataTable, ImageRef, PatchSet, StructuredData

Output types: Markdown, JSON, String, ReviewReport, SecurityReport, Notification, SlackMessage, DiscordMessage, OperationStatus, TestResult, DeploymentStatus, LintReport, Summary, TranslatedText

Context types: GitHubCredentials, GenericAPIKey, Docker, Kubernetes, AWSCredentials, SlackCredentials, Repository, CodingStandards, ShellEnvironment, UserPreferences, ConversationHistory, PromptContext, APICredentials

Step 2: Create SKILL.md (optional but recommended)

If your tool doesn't already have a SKILL.md:

---
name: your-tool-name
description: What your tool does in one line
---

## Purpose

Detailed description of what this tool does.

## When to Use

- Scenario 1
- Scenario 2

## Examples

\`\`\`bash
# Example usage
your-tool --input "example"
\`\`\`Copy

Step 3: Validate

# Install the linter
npm install -g @effectorhq/skill-lint

# Validate your SKILL.md
skill-lint .

# Run security audit
npx @effectorhq/audit scan .Copy

Step 4: Your tool is now composable

Other effector-typed tools can discover and compose with yours:

import { isTypeCompatible } from '@effectorhq/core/types';

// Check if tool A's output can feed into tool B's input
isTypeCompatible(toolA.interface.output, toolB.interface.input);
// → true or falseCopy

What Changes (and What Doesn't)

Your MCP tool continues to work exactly as before. The effector.toml is a sidecar manifest that adds metadata without changing behavior.