Agent Skills: Xcode MCP

Xcode MCP

You MUST use this skill for ANY Xcode MCP interaction — setup, tool usage, workflow patterns, or troubleshooting.

Xcode ships an MCP server exposing IDE tools to external AI clients. xcrun mcpbridge is the stdio transport clients register, available since Xcode 26.3. Xcode 27 adds an explicit "Allow external agents to use Xcode tools" gate, the run-agent launch path, an agent-extension model (custom MCP servers, skills, plug-ins), and a headless server. This skill suite covers setup, tool reference, workflow patterns, and troubleshooting.

On Xcode 26.x, mcpbridge requires a running Xcode with a project open. If that's a liability, the device/simulator half of these operations has a fully Xcode-independent CLI path: devicectl + simctl + Axiom's xcui/xclog/xcsym/xcprof. See axiom-tools (skills/device-control-ref.md).

That constraint is gone on Xcode 27. xcrun mcp-server runs the tool service with Xcode.app closed — sudo xcrun mcp-server enable, then start and open <path>. Clients still register xcrun mcpbridge; the bridge is the transport, mcp-server is the service. Apple's tool schemas describe workspaceIdentifier as "used in headless mode", so headless is a supported model rather than a workaround.

Choose between MCP and the CLI tools (devicectl, simctl, and Axiom's xcui/xclog/xcsym/xcprof) on capability, not uptime. xcui asserts, waits, toggles accessibility settings, and computes VoiceOver announcements, and none of them need sudo — which still matters in CI, where the headless server's sudo opt-in may not be available. The IDE-authoring tools (build state, render previews) remain MCP-only; xcodebuild builds and tests but does not render previews.

When to Use

Use this skill when:

• Setting up Xcode MCP for the first time
• Configuring xcrun mcpbridge for any MCP client
• Using any Xcode MCP tool (file ops, build, test, preview)
• Building, testing, or previewing via MCP tools
• Troubleshooting mcpbridge connection issues
• Workspace targeting questions
• Permission dialog confusion
• Driving simulator input with AXe (tap/type/swipe) -> read skills/axe-ref.md

Routing Logic

1. Setup/Connection → xcode-mcp-setup

Triggers:

• First-time Xcode MCP setup
• Client-specific config (Claude Code, Cursor, Codex, VS Code, Gemini CLI)
• Connection errors ("Connection refused", "No workspaces are currently open.")
• Permission dialog confusion
• Multi-Xcode targeting (MCP_XCODE_PID)
• Schema compliance issues with strict clients
• Giving external agents access to Xcode (Intelligence settings gate)
• Launching an agent via Xcode config (xcrun mcpbridge run-agent)
• Exporting Xcode's skill bundles (xcrun agent skills export)
• Extending Xcode's agent (per-agent config files, MCP servers, plug-ins)

Read: skills/xcode-mcp-setup.md

2. Using Tools & Workflows → xcode-mcp-tools

Triggers:

• How to build/test/preview via MCP
• Workflow patterns (BuildFix loop, TestFix loop)
• Tool gotchas and anti-patterns
• Workspace targeting strategy; headless bootstrap (open or create a workspace)
• When to use MCP tools vs CLI (xcodebuild)
• Destructive operation safety (XcodeRM, XcodeMV)

Read: skills/xcode-mcp-tools.md

3. Tool API Reference → xcode-mcp-ref

Triggers:

• Specific tool parameters and schemas
• Input/output format for a tool
• "How does XcodeGrep work?"
• "What params does BuildProject take?"
• Tool category listing

Read: skills/xcode-mcp-ref.md

Decision Tree

digraph xcode_mcp_router {
    rankdir=TB;
    "User has Xcode MCP question" [shape=ellipse];
    "Setup or connection?" [shape=diamond];
    "Using tools or workflows?" [shape=diamond];
    "Need specific tool params?" [shape=diamond];

    "xcode-mcp-setup" [shape=box];
    "xcode-mcp-tools" [shape=box];
    "xcode-mcp-ref" [shape=box];

    "User has Xcode MCP question" -> "Setup or connection?";
    "Setup or connection?" -> "xcode-mcp-setup" [label="yes"];
    "Setup or connection?" -> "Using tools or workflows?" [label="no"];
    "Using tools or workflows?" -> "xcode-mcp-tools" [label="yes"];
    "Using tools or workflows?" -> "Need specific tool params?" [label="no"];
    "Need specific tool params?" -> "xcode-mcp-ref" [label="yes"];
    "Need specific tool params?" -> "xcode-mcp-tools" [label="general question"];
}

Anti-Rationalization

| Thought | Reality | |---------|---------| | "I'll just use xcodebuild directly" | MCP gives IDE state, filtered compiler diagnostics, and rendered previews that CLI doesn't expose | | "I already know how to set up MCP" | Client configs differ. Permission dialog behavior is specific. Check setup skill. | | "I can figure out the tool params" | Tool schemas have required fields and gotchas. Check ref skill. | | "One workspace is open, so I can skip the identifier" | workspaceIdentifier is required anyway, despite being absent from every required list. | | "This is just file reading, I'll use Read tool" | XcodeRead sees Xcode's project view including generated files and resolved packages |

Conflict Resolution (vs Other Routers)

| Domain | Owner | Why | |--------|-------|-----| | MCP-specific interaction (mcpbridge, mcp-server, MCP tools, workspace identifiers) | axiom-xcode-mcp | MCP protocol and tool-specific | | Xcode environment (Derived Data, zombie processes, simulators) | axiom-build | Environment diagnostics, not MCP | | Apple's bundled documentation (for-LLM guides/diagnostics) | axiom-apple-docs | Bundled docs, not MCP tool | | DocumentationSearch MCP tool usage specifically | axiom-xcode-mcp | MCP tool invocation | | Build failures diagnosed via CLI | axiom-build | Traditional build debugging | | Build failures diagnosed via MCP tools | axiom-xcode-mcp | MCP workflow patterns |

Example Invocations

User: "How do I set up Xcode MCP with Claude Code?" -> Read: skills/xcode-mcp-setup.md

User: "How do I build my project using MCP tools?" -> Read: skills/xcode-mcp-tools.md

User: "What parameters does BuildProject take?" -> Read: skills/xcode-mcp-ref.md

User: "My mcpbridge connection keeps failing" -> Read: skills/xcode-mcp-setup.md

User: "How do I target a specific workspace?" / "How do I run this without Xcode open?" -> Read: skills/xcode-mcp-tools.md

User: "Can I render SwiftUI previews via MCP?" -> Read: skills/xcode-mcp-tools.md (workflow), then skills/xcode-mcp-ref.md (params)

User: "Cursor can't parse Xcode's MCP responses" -> Read: skills/xcode-mcp-setup.md (schema compliance section)

Resources

Skills: skills/xcode-mcp-setup.md, skills/xcode-mcp-tools.md, skills/xcode-mcp-ref.md, skills/axe-ref.md