Why test with Grok?
Grok is unusual in this list because xAI exposes more than one first-class path to MCP: Remote MCP Tools on the API side, an OpenAI-compatible Responses endpoint, the Grok Build CLI, and a Connectors UI aimed at end users. That is genuinely useful and also the main source of confusion — the four paths have different auth models and different limits, and a server that works through one can fail through another. Testing the tool calls themselves first separates protocol problems from integration problems.
How Grok reaches MCP tools
- xAI Remote MCP Tools — the native API-side path, where you hand xAI your server URL directly
- The OpenAI-compatible Responses API, which lets existing OpenAI-shaped MCP clients target Grok with a base-URL change
- Grok Build CLI, for local and scripted agent runs
- The Grok Connectors UI, aimed at end users adding a server without writing code
Grok is the only model here where the translation layer differs by integration path. Remote MCP Tools hands xAI your URL and lets them do the calling; the Responses API converts tools client-side before they ever reach xAI. Same server, same model, two different conversions — which is why reproducing a bug means naming the path you used.
What goes wrong with Grok specifically
- The four integration paths do not share limits or auth behaviour. A server that connects through the Connectors UI can still fail through Remote MCP Tools, and the error surfaces differently in each.
- Search traffic for "Grok MCP connector" is dominated by people wiring Grok up to someone else’s server, not testing their own — if you are debugging a connector, the failure is usually in that server’s auth, not in Grok.
- The multi-agent Grok variant is worth a separate run if your server exposes tools that can be called in parallel; sequential-only servers can behave badly under it.
Run the same prompt against the complex-schema mock through this page, then through your own Remote MCP Tools setup. If the tool choice differs, the integration path is the variable, not your server. All the mock servers →
Grok models available here
| Model | Model ID | Credits / run |
|---|
| Grok 4.5 | x-ai/grok-4.5 | 6 |
| Grok Build 0.1 | x-ai/grok-build-0.1 | 4 |
| Grok 4.20 | x-ai/grok-4.20 | 4 |
| Grok 4.3 | x-ai/grok-4.3 | 4 |
| Grok 4.20 Multi-Agent | x-ai/grok-4.20-multi-agent | 4 |
Frequently asked questions
Does Grok support MCP?
Yes. xAI supports MCP through Remote MCP Tools on the API, an OpenAI-compatible Responses endpoint, the Grok Build CLI, and a Connectors UI. None of these is MCP-native at the model level — the tool definitions are translated — but all four can drive a remote MCP server.
How do I add a custom MCP connector to Grok?
Through the Connectors UI if you want it available in the Grok app, or by passing your server URL to Remote MCP Tools if you are working through the API. Before either, confirm the server itself answers correctly — most "connector won’t connect" reports turn out to be the server rejecting auth, not Grok. Paste the URL above to check that in isolation.
Do I need an xAI API key to test here?
No. This runs through MCP Playground, so you can see how Grok calls your tools without an xAI account. You need a key only when you wire Grok into your own product.
Which Grok integration path should I use?
Remote MCP Tools for server-side agents, the Responses API if you already have OpenAI-shaped client code, Grok Build CLI for local scripting, and Connectors for end users. The full guide walks through the trade-offs and limits of each.