feat(workflow-as-mcp): wrapping workflows in the same workspace as MCP tools to particular MCP servers

[Pbonmars-20031006]

Summary

We wrap the existing API calls as MCP tool endpoints and use them to trigger workflows from MCP servers.

Type of Change

• New feature

Testing

Tested manually with @Sg312

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Review	Updated (UTC)
docs	Skipped		Dec 26, 2025 8:33pm

[greptile-apps]

Greptile Summary

This PR adds MCP (Model Context Protocol) integration allowing workflows to be exposed as tools to external MCP clients. The implementation wraps existing workflow execution APIs as MCP-compliant JSON-RPC endpoints.

Key Changes:

• New database tables (workflow_mcp_server, workflow_mcp_tool) for managing MCP servers and tool mappings
• MCP serve endpoint at /api/mcp/serve/[serverId] implementing JSON-RPC protocol for tool listing and execution
• CRUD APIs for managing workflow MCP servers and tools with proper authentication middleware
• UI components in deployment modal for configuring workflows as MCP tools
• Added 'mcp' trigger type throughout logging and execution pipeline
• Schema conversion utilities to transform workflow input formats into MCP tool schemas

Issues Found:

• Missing timeout on workflow execution fetch call could cause indefinite hangs
• Database queries load all tools then filter in memory instead of using database-level filtering
• All workflow parameters marked as required by default with no optional field support
• Auto-sync logic in UI could cause race conditions with rapid edits

Confidence Score: 4/5

• Safe to merge with minor issues that should be addressed in follow-up
• The implementation is well-structured with proper database design, authentication middleware, and thorough validation. The critical issue is the missing timeout on workflow execution fetch calls which could cause hangs. Other issues are optimization opportunities (database filtering) and UX improvements (optional fields, race condition handling) rather than blocking problems.
• apps/sim/app/api/mcp/serve/[serverId]/route.ts needs timeout added to fetch call

Important Files Changed

Filename	Overview
apps/sim/app/api/mcp/serve/[serverId]/route.ts	New MCP protocol endpoint that exposes workflows as tools, handles JSON-RPC requests, and executes workflows via internal API calls
apps/sim/lib/mcp/workflow-tool-schema.ts	Schema conversion logic that transforms workflow input formats to MCP tool schemas; marks all fields as required by default which may be too restrictive
packages/db/schema.ts	Adds two new tables (workflow_mcp_server, workflow_mcp_tool) with proper indexes, foreign keys, and cascade deletes
apps/sim/app/api/mcp/workflow-servers/[id]/tools/route.ts	CRUD operations for MCP tools with proper validation including deployed status checks, start block verification, and workspace permission checks
apps/sim/lib/mcp/middleware.ts	New authentication middleware for MCP endpoints with permission level checks (read/write/admin) and workspace verification
apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/deploy/components/deploy-modal/components/mcp-tool/mcp-tool.tsx	UI component for configuring workflows as MCP tools with real-time syncing, multi-server deployment, and parameter description editing

Sequence Diagram

sequenceDiagram
    participant Client as MCP Client
    participant Serve as MCP Serve Route
    participant DB as Database
    participant WorkflowAPI as Workflow Execute API
    participant Executor as Workflow Executor
    
    Note over Client,Executor: MCP Tool Call Flow
    
    Client->>Serve: POST tools/call request
    Serve->>DB: Query workflow_mcp_tool table
    DB-->>Serve: Tool metadata
    
    Serve->>DB: Check workflow deployment
    DB-->>Serve: isDeployed status
    
    alt Not deployed
        Serve-->>Client: Error: Not deployed
    end
    
    Serve->>WorkflowAPI: Fetch execute endpoint
    WorkflowAPI->>Executor: Run workflow blocks
    Executor-->>WorkflowAPI: Result
    WorkflowAPI-->>Serve: Execution output
    
    Serve-->>Client: CallToolResult
    
    Note over Client,Executor: Tool Registration
    
    Client->>Serve: POST tools/list request
    Serve->>DB: Query tool schemas
    DB-->>Serve: Tools with parameters
    Serve-->>Client: ListToolsResult

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[greptile-apps]

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[icecrasher321]

@greptile

[greptile-apps]

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