Connect coding agents with the MCP server

Give Claude Code, Cursor, GitHub Copilot and other MCP clients the architecture graph ArcSync parsed from your infrastructure-as-code, so they read your real architecture instead of guessing it.

npx -y arcsync-mcpstdio · MITNode 22+

What it gives an agent

ArcSync parses Terraform, AWS CDK, CloudFormation, Pulumi, Azure ARM and Serverless Framework projects into a graph of resources and the relationships between them. The MCP server exposes that graph through seven tools. Every tool except start_parse is read-only.

Tool	What it does
`list_diagrams`	Lists the diagrams in your workspace; an optional query filters by repository, branch or path.
`get_diagram`	Returns one diagram as a Mermaid flowchart (or as JSON lists) with a link to the interactive canvas.
`describe_resource`	Describes one resource: its type, IaC attributes, and every relationship in and out.
`get_delta`	Shows what a pull request changes compared with its base branch, or what a re-parse changed.
`list_versions`	Lists a diagram's saved versions (Pro).
`start_parse`	Parses a GitHub repository into a new diagram. Uses one parse from your monthly quota.
`get_parse_status`	Reports the progress of a parse started with start_parse.

1. Create an MCP credential

Sign in at arcsync.dev and open Settings → GitHub Action credentials.
Enter a label (for example, the machine or agent it is for) and click Create MCP credential.
Copy the Client ID and Client Secret. The secret is shown once.

What an MCP credential can do

It reads your diagrams and starts parses, as you, in your current workspace. It cannot delete, edit, share, comment, upload, or touch billing. An Action credential is a separate kind, which only uploads from CI, so it will not work here.

2. Store the secret in your shell

export ARCSYNC_CLIENT_SECRET='arcsec_…'

Put it in your shell profile or secret manager, never in a file you commit.

3. Add the server to your client

Claude Code

Add this to .mcp.json at the repository root. It is safe to commit, since the secret is expanded from your shell.

{
  "mcpServers": {
    "arcsync": {
      "command": "npx",
      "args": ["-y", "arcsync-mcp"],
      "env": {
        "ARCSYNC_CLIENT_ID": "arc_…",
        "ARCSYNC_CLIENT_SECRET": "${ARCSYNC_CLIENT_SECRET}"
      }
    }
  }
}

Or, for your user only:

claude mcp add arcsync -e ARCSYNC_CLIENT_ID=arc_… -e ARCSYNC_CLIENT_SECRET="$ARCSYNC_CLIENT_SECRET" -- npx -y arcsync-mcp

Cursor

Add the same mcpServers entry to .cursor/mcp.json.

VS Code (GitHub Copilot)

{
  "servers": {
    "arcsync": {
      "command": "npx",
      "args": ["-y", "arcsync-mcp"],
      "env": {
        "ARCSYNC_CLIENT_ID": "arc_…",
        "ARCSYNC_CLIENT_SECRET": "${env:ARCSYNC_CLIENT_SECRET}"
      }
    }
  }
}

4. Teach the agent when to use it

The server sends the agent short usage instructions when it connects. For Claude Code you can also add the agent skill, which says when to call each tool:

mkdir -p .claude/skills/arcsync-mcp
curl -fsSL https://arcsync.dev/docs/mcp-skill.md -o .claude/skills/arcsync-mcp/SKILL.md

Then ask, for example, “What does this PR change in our infrastructure?” or “What can the orders Lambda reach?”

Configuration

Variable	Required	Description
`ARCSYNC_CLIENT_ID`	yes	The MCP credential's client ID (`arc_…`).
`ARCSYNC_CLIENT_SECRET`	yes	The MCP credential's secret (`arcsec_…`).
`ARCSYNC_ORG`	no	Workspace (org) id to act in, when you belong to more than one. Defaults to your current workspace.
`ARCSYNC_API_URL`	no	API base URL, default `https://api.arcsync.dev`; must be https.
`ARCSYNC_APP_URL`	no	Base for canvas links, default `https://arcsync.dev`.

Plans and quotas

The server works on every plan. start_parse spends a parse from the same monthly quota as the web app; CDK and Pulumi projects also spend a server-side synth. Version history (list_versions, get_delta with a version) and the per-resource pull-request delta are Pro features. On Free, get_delta returns counts only.

Troubleshooting

“ArcSync rejected ARCSYNC_CLIENT_ID / ARCSYNC_CLIENT_SECRET”: the credential was revoked or mistyped. Create a new MCP credential.
“Check that it was created as an MCP credential”: the credential is an Action credential. Create an MCP credential instead.
A private repository's diagram is not found: diagrams belong to a workspace. Set ARCSYNC_ORG, or switch your current workspace in the web app.
start_parse fails on a private repository: install the ArcSync GitHub App on it from Settings first.

Agent-readable version of this page: /docs/mcp.md. See also theGitHub Action setup guide.