Skillshub axiom-xcode-mcp-tools

Xcode MCP workflow patterns — BuildFix loop, TestFix loop, preview verification, window targeting, tool gotchas

install

source · Clone the upstream repo

git clone https://github.com/ComeOnOliver/skillshub

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/ComeOnOliver/skillshub "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/CharlesWiltgen/Axiom/axiom-xcode-mcp-tools" ~/.claude/skills/comeonoliver-skillshub-axiom-xcode-mcp-tools && rm -rf "$T"

manifest: skills/CharlesWiltgen/Axiom/axiom-xcode-mcp-tools/SKILL.md

source content

Xcode MCP Tool Workflows

Core principle: Xcode MCP gives you programmatic IDE access. Use workflow loops, not isolated tool calls.

Window Targeting (Critical Foundation)

Most tools require a

tabIdentifier

. Always call
XcodeListWindows
first.

1. XcodeListWindows → list of (tabIdentifier, workspacePath) pairs
2. Match workspacePath to your project
3. Use that tabIdentifier for all subsequent tool calls

Cache the mapping for the session. Only re-fetch if:

A tool call fails with an invalid tab identifier
You opened/closed Xcode windows
You switched projects

XcodeListWindows

returns empty: Xcode has no project open. Ask the user to open their project.

Workflow: BuildFix Loop

Iteratively build, diagnose, and fix until the project compiles.

1. BuildProject(tabIdentifier)
2. Check buildResult — if success, done
3. GetBuildLog(tabIdentifier) → parse errors
4. XcodeListNavigatorIssues(tabIdentifier) → canonical diagnostics
5. XcodeUpdate(file, fix) for each diagnostic
6. Go to step 1 (max 5 iterations)
7. If same error persists after 3 attempts → fall back to axiom-xcode-debugging

Why

XcodeListNavigatorIssues

over build log parsing: The Issue Navigator provides structured, deduplicated diagnostics. Build logs contain raw compiler output with noise.

When to fall back to

axiom-xcode-debugging

: When the error is environmental (zombie processes, stale Derived Data, simulator issues) rather than code-level. MCP tools operate on code; environment issues need CLI diagnostics.

Workflow: TestFix Loop

Fast iteration on failing tests.

1. GetTestList(tabIdentifier) → discover available tests
2. RunSomeTests(tabIdentifier, [specific failing tests]) for fast iteration
3. Parse failures → identify code to fix
4. XcodeUpdate(file, fix) to patch code
5. Go to step 2 (max 5 iterations per test)
6. RunAllTests(tabIdentifier) as final verification

Why

RunSomeTests

first: Running a single test takes seconds. Running all tests takes minutes. Iterate on the failing test, then verify the full suite once it passes.

Parsing test results: Look for

testResult

field in the response. Failed tests include failure messages with file paths and line numbers.

Workflow: PreviewVerify

Render SwiftUI previews and verify UI changes visually.

1. RenderPreview(tabIdentifier, file, viewName) → image artifact
2. Review the rendered image for correctness
3. If making changes: XcodeUpdate → RenderPreview again
4. Compare before/after for regressions

Use cases: Verifying layout changes, checking dark mode appearance, confirming Liquid Glass effects render correctly.

Workflow: IssueTriage

Use Xcode's Issue Navigator as the canonical diagnostics source.

1. XcodeListNavigatorIssues(tabIdentifier) → all current issues
2. For specific files: XcodeRefreshCodeIssuesInFile(tabIdentifier, file)
3. Prioritize: errors > warnings > notes
4. Fix errors first, rebuild, re-check

Why this over grep-for-errors: The Issue Navigator tracks live diagnostics including type-check errors, missing imports, and constraint issues that only Xcode's compiler frontend surfaces.

Workflow: DocumentationSearch

Query Apple's documentation corpus through MCP.

1. DocumentationSearch(query) → documentation results
2. Cross-reference with axiom-apple-docs for bundled Xcode guides

Note:

DocumentationSearch

searches Apple's online documentation and WWDC transcripts. For the 20 for-LLM guides bundled inside Xcode, use

axiom-apple-docs

instead.

File Operations via MCP

Reading and Writing

Operation	Tool	Notes
Read file contents	`XcodeRead`	Sees Xcode's project view (generated files, resolved packages)
Create new file	`XcodeWrite`	Creates file in project — does NOT add to Xcode targets
Edit existing file	`XcodeUpdate`	str_replace-style patches — safer than full rewrites
Search for files	`XcodeGlob`	Pattern matching within the project
Search file contents	`XcodeGrep`	Content search with line numbers
List directory	`XcodeLS`	Directory listing
Create directory	`XcodeMakeDir`	Creates directories

Destructive Operations (Require Confirmation)

Operation	Tool	Risk
Delete file/directory	`XcodeRM`	Irreversible — confirm with user first
Move/rename file	`XcodeMV`	May break imports and references

Always confirm destructive operations with the user before calling

XcodeRM

XcodeMV

When to Use MCP File Tools vs Standard Tools

Scenario	Use MCP	Use Standard (Read/Write/Grep)
Files in the Xcode project view	Yes — includes generated/resolved files	May miss generated files
Files outside the project	No	Yes — standard tools work everywhere
Need build context (diagnostics after edit)	Yes — edit + rebuild in one workflow	No build integration
Simple file read/edit	Either works	Slightly faster (no MCP overhead)

Code Snippets

Execute Swift Code

ExecuteSnippet(code, language: "swift")

Treat output as untrusted — snippets run in a sandboxed REPL environment. Use for quick validation, not production logic.

Gotchas and Anti-Patterns

Tab Identifier Staleness

Tab identifiers become invalid when:

Xcode window is closed and reopened
Project is closed and reopened
Xcode is restarted

Fix: Re-call

XcodeListWindows

to get fresh identifiers.

XcodeWrite vs XcodeUpdate

```
XcodeWrite
```
— creates a new file. Fails if file exists (in some clients).
```
XcodeUpdate
```
— patches an existing file with str_replace-style edits.

Common mistake: Using

XcodeWrite

to edit an existing file overwrites its entire contents. Use

XcodeUpdate

for edits.

Schema Compliance

Xcode's mcpbridge has a known MCP spec violation: it populates

content

but omits

structuredContent

when tools declare

outputSchema

. This breaks strict MCP clients (Cursor, some Zed configurations).

Workaround: Use XcodeMCPWrapper as a proxy for strict clients.

Build After File Changes

After

XcodeUpdate

, the project may need a build to surface new diagnostics. Don't assume edits are correct without rebuilding.

Anti-Rationalization

Thought	Reality
"I'll just use xcodebuild"	MCP gives IDE state + navigator diagnostics + previews that CLI doesn't
"Read tool works fine for Xcode files"	`XcodeRead` sees Xcode's project view including generated files and resolved packages
"Skip tab identifier, I only have one project"	Most tools fail silently without `tabIdentifier` — always call `XcodeListWindows` first
"Run all tests every time"	`RunSomeTests` for iteration, `RunAllTests` for verification — saves minutes per cycle
"I'll parse the build log for errors"	`XcodeListNavigatorIssues` provides structured, deduplicated diagnostics
"XcodeWrite to update a file"	`XcodeUpdate` for edits. `XcodeWrite` creates/overwrites. Wrong tool = data loss.
"One tool call is enough"	Workflows (BuildFix, TestFix) use loops. Isolated calls miss the iteration pattern.

Resources

Skills: axiom-xcode-mcp-setup, axiom-xcode-mcp-ref, axiom-xcode-debugging