RFC: Sim MCP - Model Context Protocol Server for Sim

[PlaneInABottle]

Hey team,

I'm building an MCP (Model Context Protocol) stdio server that exposes Sim workflow operations to MCP clients. Wanted to share what I've got and get your thoughts.

---

What is this?

The sim-mcp server allows AI assistants (like Claude Desktop, Cursor) to interact with Sim workflows programmatically. It's a TypeScript CLI server that forwards MCP requests to the Sim backend API.

---

Current Tools (~30)

Workflow Lifecycle:

• list_workflows, get_workflow, create_workflow, delete_workflow
• get_workflow_status, get_deployed_workflow_state
• deploy_workflow, undeploy_workflow

Deployment Versions:

• list_deployment_versions, get_deployment_version
• activate_deployment_version, revert_workflow_to_deployment_version

Execution:

• execute_workflow, run_workflow_until_block, run_from_block
• run_block, cancel_execution
• get_execution_logs, get_execution_log_detail

Graph Editing:

• get_block, add_blocks, remove_blocks
• update_block_name, toggle_block_enabled, update_block_parent
• add_edge, remove_edge
• add_variable, remove_variable
• update_subflow

Workspace Assets:

• list_custom_tools, get_custom_tool, upsert_custom_tools
• list_skills, get_skill, create_skill, update_skill, delete_skill

---

Auth

Uses API key auth via x-api-key header:

• SIM_API_BASE_URL
• SIM_API_KEY

---

Questions

1. Any missing operations you'd like to see?
2. Any concerns with the auth approach?
3. Open to featuring this anywhere?
4. Any upcoming API changes I should know about?

Cheers

[PlaneInABottle]

I also take care of the output size. It won't bloat the ai with too long redundant response, except for the get log operations. I am actively using it to develop workflows and it looks great actually. I also believe it would help the publicity of the sim project, especially among developers.

[PlaneInABottle]

I did develop some endpoints without plan, I am planning to open prs for those as well, but I am not sure about the architecture since sim has some admin endpoints which normal api keys wouldn't work. Let me know what do you think about this. Maybe I could introduce 2 different api keys one for admin endpoints if user is admin etc. However I suspect the project is improving quickly so it could break often. Idk, just some thoughts.

[Sg312]

Hey! This seems pretty cool. We already have an mcp server for sim here, which handles workflow building and a variety of other operations across sim, and we're adding a lot to it soon too. Your approach seems pretty cool though, so happy to discuss further. Just wanted to link the current MCP in case you hadn't gotten a chance to check it out yet

[PlaneInABottle]

@Sg312 I didn't know you could use your copilot as a mcp server, alas it's a paid service.