Add MCP server exposing workflow engine to AI assistants

Makefile

@@ -15,6 +15,10 @@ build-ui:
 build-go:
 	go build -o server ./cmd/server
 
+# Build MCP server binary
+build-mcp:
+	go build -o workflow-mcp-server ./cmd/mcp
+
 # Run all tests with race detection
 test:
 	go test -race ./...

cmd/mcp/main.go

@@ -0,0 +1,39 @@
+// Command mcp starts the workflow MCP (Model Context Protocol) server.
+//
+// The server runs over stdio by default, making it compatible with any
+// MCP-capable AI client. It exposes workflow engine tools (validate,
+// list types, generate schemas) and resources (documentation, examples).
+//
+// Usage:
+//
+//	workflow-mcp-server [options]
+//
+// Options:
+//
+//	-plugin-dir string   Plugin data directory (default "data/plugins")
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+
+	workflowmcp "github.com/GoCodeAlone/workflow/mcp"
+)
+
+func main() {
+	pluginDir := flag.String("plugin-dir", "data/plugins", "Plugin data directory")
+	showVersion := flag.Bool("version", false, "Show version and exit")
+	flag.Parse()
+
+	if *showVersion {
+		fmt.Printf("workflow-mcp-server %s\n", workflowmcp.Version)
+		os.Exit(0)
+	}
+
+	srv := workflowmcp.NewServer(*pluginDir)
+	if err := srv.ServeStdio(); err != nil {
+		fmt.Fprintf(os.Stderr, "MCP server error: %v\n", err)
+		os.Exit(1)
+	}
+}

docs/mcp.md

@@ -0,0 +1,164 @@
+# MCP Server for Workflow Engine
+
+The workflow engine includes a built-in [Model Context Protocol (MCP)](https://modelcontextprotocol.io/) server that exposes engine functionality to AI assistants and tools.
+
+## Features
+
+The MCP server provides:
+
+### Tools
+
+| Tool | Description |
+|------|-------------|
+| `list_module_types` | List all available module types for workflow YAML configs |
+| `list_step_types` | List all pipeline step types |
+| `list_trigger_types` | List all trigger types (http, schedule, event, eventbus) |
+| `list_workflow_types` | List all workflow handler types |
+| `generate_schema` | Generate JSON Schema for workflow config files |
+| `validate_config` | Validate a workflow YAML configuration string |
+| `inspect_config` | Inspect a config and get structured summary of modules, workflows, triggers |
+| `list_plugins` | List installed external plugins |
+| `get_config_skeleton` | Generate a skeleton YAML config for given module types |
+
+### Resources
+
+| Resource | Description |
+|----------|-------------|
+| `workflow://docs/overview` | Engine overview documentation |
+| `workflow://docs/yaml-syntax` | YAML configuration syntax guide |
+| `workflow://docs/module-reference` | Dynamic module type reference |
+
+## Building
+
+```bash
+# Build the MCP server binary
+make build-mcp
+
+# Or directly with Go
+go build -o workflow-mcp-server ./cmd/mcp
+```
+
+## Installation
+
+### Claude Desktop
+
+Add the following to your Claude Desktop configuration file:
+
+**macOS**: `~/Library/Application Support/Claude/claude_desktop_config.json`
+**Windows**: `%APPDATA%\Claude\claude_desktop_config.json`
+
+```json
+{
+  "mcpServers": {
+    "workflow": {
+      "command": "/path/to/workflow-mcp-server",
+      "args": ["-plugin-dir", "/path/to/data/plugins"]
+    }
+  }
+}
+```
+
+### VS Code with GitHub Copilot
+
+Add to your VS Code `settings.json`:
+
+```json
+{
+  "github.copilot.chat.mcpServers": {
+    "workflow": {
+      "command": "/path/to/workflow-mcp-server",
+      "args": ["-plugin-dir", "/path/to/data/plugins"]
+    }
+  }
+}
+```
+
+### Cursor
+
+Add to your Cursor MCP configuration (`.cursor/mcp.json`):
+
+```json
+{
+  "mcpServers": {
+    "workflow": {
+      "command": "/path/to/workflow-mcp-server",
+      "args": ["-plugin-dir", "/path/to/data/plugins"]
+    }
+  }
+}
+```
+
+### Generic MCP Client
+
+The server communicates over **stdio** using JSON-RPC 2.0. Any MCP-compatible client can connect:
+
+```bash
+./workflow-mcp-server -plugin-dir ./data/plugins
+```
+
+## Usage Examples
+
+Once connected, the AI assistant can use the tools to:
+
+### List available module types
+```
+Use the list_module_types tool to see what modules are available.
+```
+
+### Validate a configuration
+```
+Validate this workflow config:
+modules:
+  - name: webServer
+    type: http.server
+    config:
+      address: ":8080"
+```
+
+### Generate a config skeleton
+```
+Generate a skeleton config with http.server, http.router, and http.handler modules.
+```
+
+### Inspect a configuration
+```
+Inspect this config and show me the dependency graph...
+```
+
+## Command Line Options
+
+```
+Usage: workflow-mcp-server [options]
+
+Options:
+  -plugin-dir string   Plugin data directory (default "data/plugins")
+  -version             Show version and exit
+```
+
+## Dynamic Updates
+
+The MCP server dynamically reflects the current state of the engine:
+
+- **Module types** are read from the schema registry, which includes both built-in types and any dynamically registered plugin types
+- **Plugin list** scans the configured plugin directory at query time
+- **Schema generation** uses the current module schema registry
+- **Validation** uses the same validation logic as `wfctl validate`
+
+This means the MCP server automatically picks up new module types and plugins without requiring a restart.
+
+## Running Tests
+
+```bash
+go test -v ./mcp/
+```
+
+## Architecture
+
+```
+cmd/mcp/main.go      → Entry point (stdio transport)
+mcp/server.go        → MCP server setup, tool handlers, resource handlers
+mcp/docs.go          → Embedded documentation content
+mcp/server_test.go   → Unit tests
+```
+
+The server uses the [mcp-go](https://github.com/mark3labs/mcp-go) library for MCP protocol implementation over stdio transport.

go.mod

@@ -43,6 +43,7 @@ require (
 	github.com/jackc/pgx/v5 v5.7.5
 	github.com/launchdarkly/go-sdk-common/v3 v3.5.0
 	github.com/launchdarkly/go-server-sdk/v7 v7.14.5
+	github.com/mark3labs/mcp-go v0.27.0
 	github.com/nats-io/nats.go v1.48.0
 	github.com/prometheus/client_golang v1.19.1
 	github.com/redis/go-redis/v9 v9.18.0
@@ -54,6 +55,8 @@ require (
 	go.opentelemetry.io/otel/trace v1.40.0
 	golang.org/x/crypto v0.48.0
 	golang.org/x/oauth2 v0.35.0
+	golang.org/x/sync v0.19.0
+	golang.org/x/text v0.34.0
 	golang.org/x/time v0.14.0
 	google.golang.org/api v0.265.0
 	google.golang.org/grpc v1.79.1
@@ -186,7 +189,9 @@ require (
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
 	github.com/robfig/cron/v3 v3.0.1 // indirect
 	github.com/ryanuber/go-glob v1.0.0 // indirect
+	github.com/spf13/cast v1.7.1 // indirect
 	github.com/spiffe/go-spiffe/v2 v2.6.0 // indirect
+	github.com/yosida95/uritemplate/v3 v3.0.2 // indirect
 	github.com/yuin/gopher-lua v1.1.1 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
 	go.opentelemetry.io/contrib/detectors/gcp v1.39.0 // indirect
@@ -200,9 +205,7 @@ require (
 	go.uber.org/zap v1.27.0 // indirect
 	golang.org/x/exp v0.0.0-20251023183803-a4bb9ffd2546 // indirect
 	golang.org/x/net v0.50.0 // indirect
-	golang.org/x/sync v0.19.0 // indirect
 	golang.org/x/sys v0.41.0 // indirect
-	golang.org/x/text v0.34.0 // indirect
 	google.golang.org/genproto v0.0.0-20260128011058-8636f8732409 // indirect
 	google.golang.org/genproto/googleapis/api v0.0.0-20260203192932-546029d2fa20 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20260217215200-42d3e9bedb6d // indirect

go.sum

@@ -199,6 +199,8 @@ github.com/felixge/httpsnoop v1.0.4 h1:NFTV2Zj1bL4mc9sqWACXbQFVBBg2W3GPvqp8/ESS2
 github.com/felixge/httpsnoop v1.0.4/go.mod h1:m8KPJKqk1gH5J9DgRY2ASl2lWCfGKXixSwevea8zH2U=
 github.com/fortytw2/leaktest v1.3.0 h1:u8491cBMTQ8ft8aeV+adlcytMZylmA5nnwwkRZjI8vw=
 github.com/fortytw2/leaktest v1.3.0/go.mod h1:jDsjWgpAGjm2CA7WthBh/CdZYEPF31XHquHwclZch5g=
+github.com/frankban/quicktest v1.14.6 h1:7Xjx+VpznH+oBnejlPUj8oUpdxnVs4f8XU8WnHkI4W8=
+github.com/frankban/quicktest v1.14.6/go.mod h1:4ptaffx2x8+WTWXmUCuVU6aPUX1/Mz7zb5vbUoiM6w0=
 github.com/fsnotify/fsnotify v1.9.0 h1:2Ml+OJNzbYCTzsxtv8vKSFD9PbJjmhYF14k/jKC7S9k=
 github.com/fsnotify/fsnotify v1.9.0/go.mod h1:8jBTzvmWwFyi3Pb8djgCCO5IBqzKJ/Jwo8TRcHyHii0=
 github.com/github/copilot-sdk/go v0.1.23 h1:uExtO/inZQndCZMiSAA1hvXINiz9tqo/MZgQzFzurxw=
@@ -354,6 +356,8 @@ github.com/launchdarkly/go-test-helpers/v3 v3.1.0 h1:E3bxJMzMoA+cJSF3xxtk2/chr1z
 github.com/launchdarkly/go-test-helpers/v3 v3.1.0/go.mod h1:Ake5+hZFS/DmIGKx/cizhn5W9pGA7pplcR7xCxWiLIo=
 github.com/mailru/easyjson v0.7.7 h1:UGYAvKxe3sBsEDzO8ZeWOSlIQfWFlxbzLZe7hwFURr0=
 github.com/mailru/easyjson v0.7.7/go.mod h1:xzfreul335JAWq5oZzymOObrkdz5UnU4kGfJJLY9Nlc=
+github.com/mark3labs/mcp-go v0.27.0 h1:iok9kU4DUIU2/XVLgFS2Q9biIDqstC0jY4EQTK2Erzc=
+github.com/mark3labs/mcp-go v0.27.0/go.mod h1:rXqOudj/djTORU/ThxYx8fqEVj/5pvTuuebQ2RC7uk4=
 github.com/mattn/go-colorable v0.1.9/go.mod h1:u6P/XSegPjTcexA+o6vUJrdnUu04hMope9wVRipJSqc=
 github.com/mattn/go-colorable v0.1.12/go.mod h1:u5H1YNBxpqRaxsYJYSkiCWKzEfiAb1Gb520KVy5xxl4=
 github.com/mattn/go-colorable v0.1.14 h1:9A9LHSqF/7dyVVX6g0U9cwm9pG3kP9gSzcuIPHPsaIE=
@@ -439,6 +443,8 @@ github.com/ryanuber/go-glob v1.0.0/go.mod h1:807d1WSdnB0XRJzKNil9Om6lcp/3a0v4qIH
 github.com/sirupsen/logrus v1.7.0/go.mod h1:yWOB1SBYBC5VeMP7gHvWumXLIWorT60ONWic61uBYv0=
 github.com/sirupsen/logrus v1.9.3 h1:dueUQJ1C2q9oE3F7wvmSGAaVtTmUizReu6fjN8uqzbQ=
 github.com/sirupsen/logrus v1.9.3/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
+github.com/spf13/cast v1.7.1 h1:cuNEagBQEHWN1FnbGEjCXL2szYEXqfJPbP2HNUaca9Y=
+github.com/spf13/cast v1.7.1/go.mod h1:ancEpBxwJDODSW/UG4rDrAqiKolqNNh2DX3mk86cAdo=
 github.com/spf13/pflag v1.0.7 h1:vN6T9TfwStFPFM5XzjsvmzZkLuaLX+HS+0SeFLRgU6M=
 github.com/spf13/pflag v1.0.7/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/spiffe/go-spiffe/v2 v2.6.0 h1:l+DolpxNWYgruGQVV0xsfeya3CsC7m8iBzDnMpsbLuo=
@@ -465,6 +471,8 @@ github.com/valyala/bytebufferpool v1.0.0 h1:GqA5TC/0021Y/b9FG4Oi9Mr3q7XYx6Kllzaw
 github.com/valyala/bytebufferpool v1.0.0/go.mod h1:6bBcMArwyJ5K/AmCkWv1jt77kVWyCJ6HpOuEn7z0Csc=
 github.com/wsxiaoys/terminal v0.0.0-20160513160801-0940f3fc43a0 h1:3UeQBvD0TFrlVjOeLOBz+CPAI8dnbqNSVwUwRrkp7vQ=
 github.com/wsxiaoys/terminal v0.0.0-20160513160801-0940f3fc43a0/go.mod h1:IXCdmsXIht47RaVFLEdVnh1t+pgYtTAhQGj73kz+2DM=
+github.com/yosida95/uritemplate/v3 v3.0.2 h1:Ed3Oyj9yrmi9087+NczuL5BwkIc4wvTb5zIM+UJPGz4=
+github.com/yosida95/uritemplate/v3 v3.0.2/go.mod h1:ILOh0sOhIJR3+L/8afwt/kE++YT040gmv5BQTMR2HP4=
 github.com/yuin/goldmark v1.3.5/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 github.com/yuin/gopher-lua v1.1.1 h1:kYKnWBjvbNP4XLT3+bPEwAXJx262OhaHDWDVOPjL46M=