Workflows MCP Server

Overview

A declarative workflow library for LLM agents, backed by local YAML files. Store, list, and retrieve named, versioned multi-step playbooks — each a sequence of MCP server/tool calls — for permanent reuse or one-shot temporary runs. Runs as a stdio process or a local Streamable HTTP server; an in-memory index rebuilds automatically as files change.

Tools

Capability reference

workflow_list tool

• Optional query (name and description), category (substring), and tags (all must match) filters, case-insensitive; temporary drafts are never listed
• Sorted by name, then highest version first; an empty result carries a notice echoing the applied filters
• includeTools: true adds each workflow's unique server/tool pairs

workflow_get tool

• name plus an optional semver version; omit version for the highest available, drafts included
• Returns the full workflow, its source (permanent or temp), and globalInstructions from global_instructions.md (null when absent); fails with not_found or version_not_found
• Template placeholders such as {{input.foo}} come back verbatim — the server never interpolates them

workflow_create tool

• name, semver version, description, author, category, and steps (plus optional tags); stored as one file per name@version under categories/<category>/, with created and updated dates stamped
• Returns the key (name@version) and filePath; fails with already_exists when a permanent workflow or a draft holds the key, invalid_input, or write_failed

workflow_create_temp tool

• The workflow_create fields minus category; stored under temp/, retrievable with workflow_get, never listed, and kept until workflow_delete removes it
• status is created, or overwritten when it replaced the draft of the same key (keeping that draft's created_date); a key held by a permanent workflow fails with already_exists

workflow_delete tool

• name plus an optional version (omitted: the highest across permanent workflows and drafts); the user confirms the resolved name@version, source, and file before anything is deleted, so a client without elicitation cannot delete
• Returns the deleted workflow's source, plus a notice when another file declaring the same key now takes its place; fails with cancelled, confirmation_invalid (a prompt never issued, already answered, older than 10 minutes, or issued to another caller), target_changed (the file or its content changed after the user saw it), or not_found

Features

Built on @cyanheads/mcp-ts-core: stdio and Streamable HTTP transports, pluggable auth (none / jwt / oauth), swappable storage (in-memory, filesystem, Supabase, Cloudflare KV/R2/D1), structured logging with optional OpenTelemetry tracing.

Workflow library:

• YAML files under categories/ and temp/ are validated at index time; an invalid file is skipped and logged, never crashes the server
• In-memory index keyed by name@version, read from each file's content rather than its name and kept fresh by a debounced recursive watcher; a permanent workflow outranks a draft with the same key
• Versions are canonical semver everywhere: a leading v, surrounding whitespace, and build metadata are dropped, so v1.0.0+build.5 is stored, keyed, and looked up as 1.0.0
• Creates and deletes run one at a time, so each existence check holds until its write lands; filenames carry a hash of name@version, so keys whose slugs coincide never share a file
• An _index.json snapshot is written on every rebuild for external tooling and debugging

Agent-friendly output:

• Discriminated output — source: "permanent" | "temp" on every workflow_get response and typed reason codes (not_found, version_not_found, already_exists, cancelled, confirmation_invalid, target_changed, index_unavailable, …) on failures, so callers branch on data instead of parsing error strings
• No extra round trip — workflow_get always returns globalInstructions alongside the workflow definition in the same response
• Response shaping — workflow_list's optional includeTools flag pre-derives the unique server/tool pairs used by a workflow, and an empty result echoes the applied filters with a broadening hint instead of returning nothing

Getting started

No API keys required. The server reads from a local workflows-yaml/ directory by default.

Add the following to your MCP client configuration file:

{
  "mcpServers": {
    "workflows-mcp-server": {
      "type": "stdio",
      "command": "bunx",
      "args": ["@cyanheads/workflows-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "WORKFLOWS_DIR": "/absolute/path/to/your/workflows-yaml"
      }
    }
  }
}

Or with npx (no Bun required):

{
  "mcpServers": {
    "workflows-mcp-server": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@cyanheads/workflows-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "WORKFLOWS_DIR": "/absolute/path/to/your/workflows-yaml"
      }
    }
  }
}

Or with Docker:

{
  "mcpServers": {
    "workflows-mcp-server": {
      "type": "stdio",
      "command": "docker",
      "args": [
        "run", "-i", "--rm",
        "-e", "MCP_TRANSPORT_TYPE=stdio",
        "-v", "/absolute/path/to/your/workflows-yaml:/workflows-yaml",
        "-e", "WORKFLOWS_DIR=/workflows-yaml",
        "ghcr.io/cyanheads/workflows-mcp-server:latest"
      ]
    }
  }
}

For Streamable HTTP, set the transport and start the server:

MCP_TRANSPORT_TYPE=http MCP_HTTP_PORT=3010 bun run start:http
# Server listens at http://localhost:3010/mcp

Seed workflows

The repository ships a workflows-yaml/ directory with example workflows organized under categories/. These are ready to use as a starting point. The workflows-yaml/global_instructions.md file contains instructions the server prepends to every workflow_get response — edit it to set global guidance for your agent.

Prerequisites

• Bun v1.4.0 or higher (or Node.js v24+).
• A local directory containing YAML workflow files (or use the bundled workflows-yaml/ seed).

Installation

1. Clone the repository:

git clone https://github.com/cyanheads/workflows-mcp-server.git

1. Navigate into the directory:

cd workflows-mcp-server

1. Install dependencies:

bun install

1. Configure environment:

cp .env.example .env
# edit .env if needed — most settings have defaults

Configuration

See .env.example for the full list of optional overrides.

Running the server

Local development

• Build and run:

  # One-time build
  bun run rebuild
  
  # Run the built server
  bun run start:stdio
  # or
  bun run start:http
  

• Run checks and tests:

  bun run devcheck   # Lint, format, typecheck, security
  bun run test       # Vitest test suite
  bun run lint:mcp   # Validate MCP definitions against spec
  

Docker

docker build -t workflows-mcp-server .
docker run --rm \
  -v /path/to/workflows-yaml:/workflows-yaml \
  -e WORKFLOWS_DIR=/workflows-yaml \
  -p 3010:3010 \
  workflows-mcp-server

The Dockerfile defaults to HTTP transport, stateful session mode (required — see MCP_SESSION_MODE above), and logs to /var/log/workflows-mcp-server. OpenTelemetry peer dependencies are installed by default — build with --build-arg OTEL_ENABLED=false to omit them.

Project structure

Development guide

See CLAUDE.md for development guidelines and architectural rules. The short version:

• Handlers throw, framework catches — no try/catch in tool logic
• Use ctx.log for request-scoped logging
• Register new tools via the barrel in src/mcp-server/tools/definitions/index.ts
• Filesystem operations go through WorkflowIndexService, not directly in tool handlers

Contributing

Issues are welcome. Run checks and tests before submitting:

bun run devcheck
bun run test

License

Apache-2.0 — see LICENSE for details.