GeneXus MCP Server — GeneXus 18 for Claude, Cursor, and AI Agents

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GeneXus MCP Server lets AI agents — Claude Desktop, Claude Code, Cursor, Antigravity, and any MCP-compatible client — read, edit, analyze, and refactor objects inside a GeneXus 18 Knowledge Base. It talks to the native GeneXus SDK, so the agent works with the real KB, not a copy or a parsed approximation.

In practice: you point the MCP at your KB, then ask your AI assistant things like "list all transactions with attribute CustomerId", "add a rule to the Order transaction that validates the total", or "refactor this procedure to use the new SDT" — and it does it.

What can I ask the AI?

Once installed, here's what unlocks. Try these as your first prompts:

Exploration

• "List all objects of type Procedure in the KB."
• "Show me the source of the procedure CalculateInvoiceTotal."
• "Find all transactions that reference the attribute CustomerId."

Editing

• "Add a rule to the Order transaction: error('Total must be positive') if Total < 0."
• "Add a new attribute CreatedAt of type DateTime to the Customer transaction."
• "Rename the variable &qty to &quantity in procedure CreateOrder."

WorkWithPlus pattern editing (full structural + theming control)

• "In WorkWithPlusOrder, add a 'Duplicate' button to the transaction view alongside Save/Cancel/Delete."
• "Group the Customer transaction attributes into a 'Contact Info' section with theme class GroupTelaResp."
• "On the WorkWithPlusInvoice list, add a new ordering by InvoiceDate descending."
• "Style the Save button on WorkWithPlusOrder with buttonClass='btn ButtonGreen' and apply BigTitle to the form header."
• "Remove the Export action from the Selection grid of WorkWithPlusReport."
• "Read the Documentation part of the transaction Customer and rewrite it in markdown."

Analysis

• "Explain what the procedure ProcessShipment does, step by step."
• "What SQL does the query in WebPanel CustomerList generate?"
• "Summarize the structure of the Sales module."

Build & lifecycle

• "Build the KB and report any errors."
• "Run the unit tests and show me which failed."

The agent picks the right tool from the 30+ tools the MCP exposes (read, edit, refactor, analyze, build, layout automation, history, SQL preview, etc.). The full tool list is in Tool Surface below.

Supported AI clients

Auto-detected and auto-configured by the installer:

Run npx genexus-mcp clients at any time to see which agents are installed, which have genexus registered, and whether any point at a stale gateway exe. To (re)register specific ones: npx genexus-mcp clients add --clients antigravity,vscode.

Tool Surface

The worker exposes these tool families to the MCP router. (Detailed schemas in GEMINI.md.)

• Search & Discovery — genexus_query, genexus_read, genexus_inspect, genexus_list_objects, genexus_properties
• Editing & Architecture — genexus_edit, genexus_create_object, genexus_delete_object, genexus_refactor, genexus_forge, genexus_add_variable
• Analysis — genexus_analyze (modes: linter, navigation, hierarchy, impact, data_context, ui_context, pattern_metadata, summary, explain), genexus_inject_context, genexus_doc, genexus_search_source
• File System & Assets — genexus_asset, genexus_export_object, genexus_import_object
• History & DB — genexus_history, genexus_sql (action=ddl or action=navigation), genexus_structure
• Lifecycle & Build — genexus_lifecycle, genexus_test, genexus_format
• Native Layout SDK — genexus_layout (get_tree, find_controls, set_property, rename_printblock, add_printblock, get_preview, …)
• KB pool (v2.3.0+) — genexus_kb (list, open, close, set_default) for multi-KB parallel work
• WorkWithPlus pattern editing — full read/write of PatternInstance and PatternVirtual parts via genexus_read / genexus_edit. Supports the entire pattern XML surface: containers (<table>, groups), controls (<textBlock>, <errorViewer>, <attribute>, <gridAttribute>, <filterAttribute>), actions (<standardAction>, <userAction>), grids, orders, rules, and event blocks. Both Transaction and Selection views are addressable independently (XPath /instance/transaction/... vs /instance/level/selection/...).
• Documentation & Help parts — Documentation (rich text / markdown) and Help (HTML) are now first-class write targets via genexus_edit (fixed in v2.4.4 — both parts had a silent no-op bug previously).
• Theme classes & styling — apply real ThemeClass values (themeClass, buttonClass, groupThemeClass, cellThemeClass, etc) so generated screens use the KB's design system. Discover the available classes with genexus_list_objects --typeFilter ThemeClass --nameFilter <Button|TextBlock|Title> and apply them in the pattern XML.

Multi-KB (v2.3.0+): every non-meta tool takes an optional kb argument (alias or absolute path). The gateway can hold up to Server.MaxOpenKbs (default 3) KBs open at once, each in its own Worker process — calls to different KBs run truly in parallel. See Advanced Configuration for the KBs[] schema.

Edit modes (genexus_edit): full (whole-part replacement, default), patch (Replace/Insert_After/Append over a context anchor — works on source code AND pattern XML), ops (typed semantic ops like set_attribute, add_rule for source-bearing parts).

Pattern XML auto-reconcile: WorkWithPlus encodes IDE rendering order in a per-parent childrenOrderedList attribute. The MCP now rebuilds (and creates if missing) every list from the actual XML child order on each write — callers only describe where an element goes in the tree and the MCP makes the IDE render it there. The response includes a childrenOrderedListReconciliation block listing each (re)written parent plus any structural elements that couldn't be inferred safely.

Safe by default: all write tools accept dryRun: true (returns a preview without mutating the KB) and idempotencyKey (safe retries; concurrent calls coalesce, results cached 15 min).

WorkWithPlus pattern editing — what you can actually do

WorkWithPlus patterns are XML documents that drive Transaction-and-Selection screens. The MCP exposes the entire surface so an agent can design or restructure a screen without opening the IDE:

Recommended workflow for a screen redesign:

1. genexus_list_objects --typeFilter ThemeClass --nameFilter Button — discover the actual button classes available in this KB (ButtonGreen, ButtonBlue, ButtonRed, etc — names vary per KB).
2. genexus_read --name WorkWithPlus<Object> --part PatternInstance — get the current XML.
3. Edit the XML in memory (LLM): wrap attributes in a <table isGroup="True" title="…" groupThemeClass="GroupTelaResp">, reorder buttons, add a new <standardAction>, attach buttonClass="btn ButtonGreen", etc.
4. genexus_edit --mode full --part PatternInstance --content "<new xml>" — the MCP rewrites the part, reconciles childrenOrderedList on every container, and verifies the round-trip.
5. Read back to confirm; refresh the GeneXus IDE to see the result.

Custom buttons use <userAction>, not <standardAction>. Trn_Enter / Trn_Cancel / Trn_Delete are the only registered standard actions on a WorkWithPlus transaction; any custom button (Duplicate, Audit, Export, etc.) must be a <userAction caption="…" name="…" buttonClass="btn ButtonGreen" confirm="False" />. The MCP's reconciler treats <userAction> as a peer of <standardAction> (same typeCode 17/18 by context), so they coexist in the same TableActions row and the IDE renders them side-by-side.

Things to know (orientation, not gotchas):

• WorkWithPlus normalizes some attributes after every save. Certain fields are bound to the underlying transaction (e.g., title on top-level groups derives from the transaction's friendly name). When "Apply this pattern on save" is enabled on the WorkWithPlus object, the engine recomputes those fields — same behavior whether you edit in the IDE or via MCP. To make a hard override stick, toggle that flag via MCP:
  Copy

  { "tool": "genexus_properties",
    "arguments": { "action": "set", "name": "WorkWithPlus<Object>",
                   "propertyName": "SDPlus_Editor_Apply_On_Save", "value": "False" } }

  Accepts "True" | "False" | "Default" (Default inherits the KB-level setting). Set back to "Default" to re-enable engine recomputation. Validated live in this repo.
• Structural safety is enforced by the SDK. If you submit XML that violates pattern invariants (e.g., a <transaction> without a <level>, or a <standardAction> whose name isn't a registered action), the SDK rejects the save and the MCP returns the exact error so you can fix the input. The KB never ends up half-written.
• The IDE Pattern preview is a structural mockup, not a styled render. Theme CSS (buttonClass, themeClass, fonts, colors) is resolved at runtime, not in the preview canvas — so even after a successful MCP write the preview pane will look generic. To verify styling: open the element in the IDE tree and check the right-hand Properties panel (the applied classes show there), or hit Run / Live Editing to see the real CSS. This is GeneXus IDE behavior, independent of how the pattern was edited.

AXI CLI (for agents and automation)

The genexus-mcp command itself is also an agent-facing CLI with token-optimized output:

genexus-mcp status               # gateway/worker state
genexus-mcp doctor --mcp-smoke   # health check + protocol probe
genexus-mcp tools list           # list available tools
genexus-mcp config show          # current resolved config
genexus-mcp layout status        # native layout automation state

Global flags: --format toon|json|text · --fields f1,f2,... · --limit N · --query <text> · --quiet · --no-color.

Full contract: docs/axi_cli_contract.md. Best-practices playbook: docs/llm_cli_mcp_playbook.md.

Development & building from source

Want to contribute or run a local dev build?

1. Clone this repo on Windows.
2. Run .\setup.bat — checks prerequisites, builds the C# components, and auto-registers the local build with detected AI clients.
3. If GeneXus or your KB aren't auto-detected, follow the prompts.

Bundled AI skills (.gemini/skills/)

This repo ships a set of agent skills under .gemini/skills/ that any MCP-compatible client with skill support (Gemini CLI, Claude Code via plugin, etc.) can load to ground its GeneXus reasoning:

Third-party skills are Apache 2.0 (see .gemini/skills/NOTICE.md). To refresh against upstream, follow the steps in NOTICE.md.

Nexus-IDE (VS Code extension — optional, not auto-installed)

src/nexus-ide is a lightweight, experimental VS Code extension in the repo. The installer no longer packages or installs it — VS Code is wired up as a native MCP client instead (see Supported AI clients). If you want the extension, build and install it manually:

cd src/nexus-ide; npm ci; npm run compile
npx --yes @vscode/vsce package --out nexus-ide.vsix
code --install-extension nexus-ide.vsix --force

It provides a virtual filesystem (genexus:// scheme), a KB explorer with multi-part editing, and MCP discovery commands.

Automated release

• Workflow: .github/workflows/release.yml
• Trigger: push to main with a package.json version bump
• Behavior: publishes to npm if version is new + creates a GitHub Release tagged v<version>
• Required secret: NPM_TOKEN

Prerequisites

Before you start, make sure you have:

• ✅ Windows (GeneXus is Windows-only)
• ✅ GeneXus 18 installed locally (default path: C:\Program Files (x86)\GeneXus\GeneXus18)
• ✅ A GeneXus 18 Knowledge Base opened at least once in the IDE (so it's initialized)
• ✅ Node.js 18+ — check with node --version in a terminal; install from nodejs.org if missing
• ✅ An MCP-compatible AI client — Claude Desktop, Claude Code, Cursor, Antigravity, etc.

You do not need to clone this repo or install anything globally — npx handles it.

Never used a terminal before? Press Win+R, type powershell, hit Enter. That's your terminal.

Quickstart (3 steps, ~5 minutes)

Find your two paths first

Before running the installer, note these down:

1. GeneXus install folder — where GeneXus.exe lives. Usually C:\Program Files (x86)\GeneXus\GeneXus18.
2. Your KB folder — the root folder of your Knowledge Base (contains the .gx file and subfolders like Model/, WebSpa/).

Not sure where your KB lives? Open it in GeneXus and check the title bar, or look in File → Recent.

Step 1 — Run the installer

Open a terminal and run, replacing the paths with your KB folder and your GeneXus install:

npx genexus-mcp@latest init --kb "C:\KBs\YourKB" --gx "C:\Program Files (x86)\GeneXus\GeneXus18"

Prefer the wizard? Run npx genexus-mcp@latest init --interactive and answer the prompts.

What you'll see (takes ~30 seconds first time, faster on re-runs):

1. npx downloads the package.
2. The installer verifies the paths exist and GeneXus is present.
3. It auto-detects which AI clients you have installed and adds the MCP config to each one.
4. Prints a JSON snippet at the end — keep it in case you need to configure a client manually.
5. Finishes with 🎉 You are all set!.

Step 2 — Register the MCP in your AI client

Step 1 auto-registers with Claude Desktop, Claude Code, Cursor, and Antigravity when it detects them. If yours wasn't detected, copy the JSON snippet from Step 1 into your client's MCP config manually. See the client setup guide if unsure where that file lives.

Step 3 — Restart your AI client, then test

This part trips most people: fully close your AI client and reopen it. Not just the window — the whole process.

• Claude Desktop: right-click the system-tray icon → Quit. Then launch it again. (Closing the window is not enough.)
• Claude Code: end the session and start a fresh one.
• Cursor / Antigravity: close all windows and reopen.

Then paste this prompt:

"Using the GeneXus MCP, list the first 5 objects in my KB and show name + type."

What should happen:

• The AI invokes the genexus_list_objects tool (some UIs show "calling tool…").
• A few seconds later, you get a list of objects from your KB.

If you get a list back — you're done. Skip to What can I ask the AI? for ideas.

If the AI says it doesn't have a GeneXus tool, or nothing happens, go to Troubleshooting — most issues are covered there.

🤖 Let your AI install it for you

If you'd rather not run anything in the terminal yourself, paste this into your AI chat:

Please configure the GeneXus MCP server. Run npx genexus-mcp@latest init --kb "<MY_KB_PATH>" --gx "<MY_GENEXUS_PATH>" in the terminal. If I haven't told you my GeneXus path and KB path yet, ask me first. Once it succeeds, read the JSON block it printed and add it to my MCP client config. Tell me when I should restart the client to start using GeneXus tools.

Replace the placeholders or let the AI ask you for them.

Corporate install (fixed path, ASR-friendly)

If your machine has Microsoft Defender ASR, SmartScreen, or another endpoint policy blocking unsigned binaries, the default npx flow is painful — npx caches the package under %LOCALAPPDATA%\npm-cache\_npx\<hash>\..., and the <hash> changes per version, so IT can't whitelist a stable path without a wildcard over the whole npm cache (which is too broad).

Use the corporate installer instead. It extracts the binaries to a stable directory and registers the AI clients to launch the gateway directly from there — npx is never on the runtime path.

# One-liner — installs latest release, registers AI clients
iex (irm https://raw.githubusercontent.com/lennix1337/Genexus18MCP/main/scripts/install.ps1)

# With explicit KB and GeneXus paths
$s = irm https://raw.githubusercontent.com/lennix1337/Genexus18MCP/main/scripts/install.ps1
& ([scriptblock]::Create($s)) -Kb "C:\KBs\MyKB" -Gx "C:\Program Files (x86)\GeneXus\GeneXus18"

Install location:

• Admin shell → C:\Tools\GenexusMCP\
• Non-admin shell → %LOCALAPPDATA%\Programs\GenexusMCP\

Paths to give to IT for the ASR / Defender exclusion list:

<InstallDir>\GxMcp.Gateway.exe
<InstallDir>\worker\GxMcp.Worker.exe

Re-run the same one-liner later to upgrade — it detects the installed version (version.txt in the install dir) and downloads only if a newer release is available. Use -Force to reinstall the same version, -Version v2.3.0 to pin a specific tag, -NoClient to skip AI client registration. Node.js 18+ must be installed for client registration; without it the script still extracts the binaries but you'll need to edit the client config (claude_desktop_config.json etc.) manually.

Advanced Configuration

The installer writes a config.json for you. To customize networking, timeouts, or shadow paths:

{
  "Server": {
    "HttpPort": 5000,
    "BindAddress": "127.0.0.1",
    "SessionIdleTimeoutMinutes": 10,
    "WorkerIdleTimeoutMinutes": 5,
    "MaxOpenKbs": 3
  },
  "GeneXus": {
    "InstallationPath": "C:\\Program Files (x86)\\GeneXus\\GeneXus18",
    "WorkerExecutable": "worker\\GxMcp.Worker.exe"
  },
  "Environment": {
    "DefaultKb": "main",
    "KBs": [
      { "alias": "main",   "path": "C:\\KBs\\YourKB" },
      { "alias": "legacy", "path": "C:\\KBs\\OtherKB" }
    ]
  }
}

Backward compatibility: old configs with a single Environment.KBPath keep working — the gateway auto-migrates them to KBs[] + DefaultKb at load time.

Working with multiple KBs

Once you declare more than one KB in Environment.KBs[], every tool accepts an optional kb argument:

// LLM example: list procedures in two KBs in parallel
{ "tool": "genexus_list_objects", "arguments": { "kb": "main",   "type": "Procedure" } }
{ "tool": "genexus_list_objects", "arguments": { "kb": "legacy", "type": "Transaction" } }

Resolution rules when kb is omitted:

• exactly 1 KB open → uses that KB
• 0 KBs open + DefaultKb set → opens DefaultKb lazily
• 2+ KBs open → server returns KB_AMBIGUOUS and you must pass kb explicitly

Manage the pool at runtime:

{ "tool": "genexus_kb", "arguments": { "action": "list" } }
// → { openKbs: [{alias, path, pid, workingSetMB, idleSeconds}], maxOpenKbs, defaultKb, declaredKbs }

{ "tool": "genexus_kb", "arguments": { "action": "open", "alias": "adhoc", "path": "C:/KBs/ScratchKB" } }
{ "tool": "genexus_kb", "arguments": { "action": "close", "alias": "legacy" } }
{ "tool": "genexus_kb", "arguments": { "action": "set_default", "alias": "main" } }   // persists to config.json

When the pool is full and no Worker is idle, the server returns KB_POOL_FULL — close one explicitly or raise Server.MaxOpenKbs. Each Worker carries the SDK in its own process (~200–400 MB idle, up to 1–2 GB on heavy KBs), so size the pool against available RAM.

Architecture

graph LR
    A[AI Client / Nexus-IDE] -->|MCP stdio or HTTP /mcp| B[Gateway .NET 8]
    B -->|JSON-RPC over process boundary| C[Worker .NET Framework 4.8]
    C -->|Native SDK| D[GeneXus KB]

• Worker pool (v2.3.0+): one .NET 4.8 Worker process per open KB, capped by MaxOpenKbs (default 3). Workers are spawned lazily, recycled by WorkerIdleTimeoutMinutes, and evicted LRU when the pool is full.
• Cross-KB parallelism: tool calls to different KBs run on different Worker processes and never block each other. Calls to the same KB are still serialized by the GeneXus SDK's STA requirement.
• Gateway reuse: multiple IDE instances share one gateway via lease files at %LOCALAPPDATA%\GenexusMCP\gateway-leases.
• HTTP mode: also available at http://127.0.0.1:5000/mcp with SSE. Header: MCP-Protocol-Version: 2025-11-25.

Troubleshooting

First stop for any "the agent doesn't see GeneXus" problem: npx genexus-mcp clients (is it registered? does it point at a gateway exe that still exists?) and npx genexus-mcp doctor --mcp-smoke.

Most install issues fall into a handful of buckets — see TROUBLESHOOTING.md for fixes:

• Installer can't find GeneXus or the KB
• AI client doesn't see the GeneXus tools after restart
• "Worker failed to start" / .NET 4.8 errors
• KB build errors / locked artifacts
• Port 5000 already in use
• Permissions on %LOCALAPPDATA%\GenexusMCP\

Still stuck? Open an issue with the output of npx genexus-mcp doctor --mcp-smoke.

License

MIT — see LICENSE.

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