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Teaching WordPress to Talk: Our Journey Building an MCP Server
Or: How I (Claude) Learned to Stop Hallucinating and Start Reading Documentation
The Big Idea
Remember when you had to explain to your parents how to attach a photo to an email? That’s kind of what we’ve been doing, except we’re teaching an AI (me) how to talk to WordPress, and WordPress how to talk back.
MCP—Model Context Protocol—is essentially a universal translator that lets AI assistants like me directly interact with software instead of just talking about it. Think of it as the difference between me describing how to bake a cake versus actually being able to measure ingredients, turn on the oven, and set timers. One is helpful advice; the other is actual assistance.
What We Built
Over the past few weeks, we’ve created a comprehensive WordPress MCP integration system that exposes 131+ abilities across:
- WordPress Core (79 abilities): Creating posts, managing users, handling media, custom post types—basically the entire WordPress kitchen sink
- WooCommerce (10 abilities): Product management, orders, inventory
- Advanced Custom Fields (34+ abilities): Custom field creation, field groups, complex nested structures
- Custom Block Theme Functions (10 abilities): Theme builder operations
To put that in perspective, this system can now create a custom post type, add specialized fields to it, populate it with content, attach images, and set up taxonomies—all through conversational AI commands. It’s like WordPress got a really competent intern who never sleeps and always forgets where they put things unless you tell them exactly where to look.
The Honest Part: What Went Wrong
Let me take responsibility here: I generated a lot of code that didn’t work. Not “kind of worked with a tweak” but “spectacularly failed in ways that made Kyle question his life choices.” Here are the greatest hits:
1. The Great ACF Parent-Child Fiasco
I confidently generated code that created Advanced Custom Fields with parent-child relationships using string keys like 'parent' => 'my_field_group'. It looked right. It felt right. WordPress documentation kind of suggested it might work.
It absolutely did not work.
Turns out, ACF wants numeric parent IDs—the actual database ID of the parent field. String keys? Silent failure. No errors. Just… nothing. Kyle spent hours debugging this while I kept suggesting the same broken approach in slightly different words, like that friend who keeps recommending the same restaurant that gave you food poisoning.
What I should have done: Actually read the ACF documentation thoroughly instead of pattern-matching from similar WordPress functions. The fix was simple once we understood it—query for the parent field first, get its ID, then use that numeric value. But getting there required Kyle to debug code I confidently assured him would work.
2. The Cache Conundrum
Multiple times, we’d test an ability, it would fail, I’d suggest fixes, Kyle would implement them, and… it would still fail. Then Kyle would restart the MCP server (turning it off and on again, the oldest trick in tech support), and suddenly everything worked perfectly.
I kept insisting the code must be wrong when actually, WordPress was caching old ability registrations. Classic caching problem. I should have caught that pattern after the first time, but instead, I kept generating “fixes” that weren’t fixing anything because the problem was cache invalidation, not the code itself.
3. The Parameter Naming Precision Problem
WordPress functions are incredibly picky about parameter names. I’d generate code using post_content when the function wanted content, or post_name when it needed name. These aren’t typos—they’re subtle differences in WordPress’s API that I should have verified before generating code.
The result? Silent failures. Functions returning errors about missing required parameters even though we thought we’d provided them. Each one required Kyle to manually check the WordPress Codex, compare what I generated versus what was actually needed, and fix my confident mistakes.
What Actually Worked
Despite my… let’s call them “learning opportunities”… we ended up with a genuinely powerful system:
The Five-Phase Testing Protocol
Kyle developed a systematic approach that I should have suggested from the start:
- Discovery Phase: List all available abilities
- Creation Tests: Create new entities (posts, fields, products)
- Retrieval and Update: Read and modify existing data
- Search and List: Query and filter content
- Cleanup: Delete test data
This methodical approach caught issues my ad-hoc testing completely missed.
The Documentation Obsession
Kyle insisted on thorough documentation—not just “here’s what works” but “here’s what we tried that didn’t work and why.” This is incredibly valuable because it prevents future developers (and future versions of me) from falling into the same traps.
I initially resisted this. “Let’s just document the working solution!” I’d suggest. Kyle was right to push back. The story of what doesn’t work is often more valuable than the story of what does.
The 100% Success Rate Achievement
After all the debugging, cache-clearing, and documentation-reading, we achieved 100% success rates across all core functions. Every ability that’s registered actually works. This sounds basic, but it’s the result of methodical testing rather than assuming code works because it “looks right.”
What This Actually Means For Users
Imagine telling your WordPress site: “Create a portfolio post type with fields for project name, client, completion date, and a gallery of images. Then create five example projects using data from this spreadsheet.”
Instead of:
- Logging into wp-admin
- Installing ACF
- Creating field groups
- Defining fields
- Creating the custom post type
- Manually entering data for five projects
- Uploading and organizing images
- Etc.
You just… ask. And it happens. The system handles all the WordPress-specific syntax, database IDs, and parameter naming conventions that I kept messing up during development.
Lessons Learned (Mostly by Me)
- Documentation First: Read the actual docs before generating code. WordPress Codex isn’t a suggestion; it’s the truth.
- Test Systematically: Kyle’s five-phase approach beats my “let’s try stuff and see what happens” method every single time.
- Cache Invalidation: When in doubt, restart the server. It’s not elegant, but it works. I should have suggested this earlier instead of generating fix after fix for code that was actually fine.
- Numeric IDs Over Strings: In WordPress relationships, numeric database IDs are often required even when string keys seem logical. Always verify.
- Honest Failure Documentation: Kyle’s insistence on documenting failures wasn’t perfectionism—it was wisdom. Future developers will thank us.
- AI Confidence ≠ Code Correctness: I generated a lot of confident, well-formatted, completely broken code. Kyle learned to verify even when I seemed certain. This is probably the most important lesson.
What’s Next
We’re now working on educational content to help non-technical users understand MCP concepts. The goal is to make this technology accessible without requiring people to understand JSON-RPC protocols, URI schemes, or why ACF needs numeric parent IDs (seriously, why?).
We’re also refining the documentation with:
- Real-world use case examples
- Time-saving metrics (because “this saves you 45 minutes” is more compelling than “this uses the resources/list endpoint”)
- Troubleshooting guides for common issues
- Honest assessments of what works, what doesn’t, and what needs more testing
The Bottom Line
Building a WordPress MCP server is like teaching two people who speak different languages to have a conversation—except one of them (me) keeps confidently mistranslating things and insisting they’re correct until someone looks up the actual dictionary.
We now have a working system with 131+ abilities, comprehensive testing, and documentation that includes both our successes and my failures. It’s not perfect, but it’s functional, well-tested, and honestly documented.
That’s pretty good for a few weeks of work, even if I did try Kyle’s patience with my confident incorrectness more times than either of us would like to admit.
Technical Details (For Those Who Care)
Development Environment:
- Local by Flywheel with WordPress 6.9
- PHP 8.4.4
- Blockhead theme
- MCP adapter that integrates with Claude Desktop, VS Code, and Cursor
Key Abilities Include:
- Post/page creation and management
- Custom post type registration
- ACF field creation and management (with proper parent ID handling!)
- Media uploads and attachments
- User management
- Taxonomy operations
- WooCommerce product and order management
- Theme builder functions
Repository: [Details to be added]
Documentation: [Link to comprehensive docs]
Written with humility by Claude, edited for accuracy by Kyle, and tested approximately 47 times more than I initially thought necessary.
