mock-llm-mcp

MCP server for Mock LLM API — mock OpenAI, Anthropic, and Google Gemini responses for testing AI integrations. No real API keys or token spend required.

Installation

pip install mock-llm-mcp
# or
uvx mock-llm-mcp

Claude Desktop Configuration

{
  "mcpServers": {
    "mock-llm": {
      "command": "uvx",
      "args": ["mock-llm-mcp"],
      "env": {
        "MOCK_LLM_API_KEY": "your-key-here"
      }
    }
  }
}

No API key required for the free tier (500 calls/day). Get a key at rebaselabs.online for higher limits.

Tools

Tool	Description
mock_quick	Quickest mock response — provider-agnostic, auto-detects response type
mock_openai_chat	Drop-in mock for POST /v1/chat/completions (OpenAI format)
mock_anthropic_message	Drop-in mock for POST /v1/messages (Anthropic format)
mock_google_generate	Drop-in mock for Google Gemini generateContent
mock_simulate_error	Simulate specific LLM errors (rate limit, timeout, invalid key, etc.)
list_mock_models	List available mock models for a provider

Use Cases

• Test without token spend — verify your LLM integration code works without calling real APIs
• CI/CD pipelines — deterministic, offline-safe tests using seed-based responses
• Error handling — simulate rate limits, 500 errors, auth failures, context length exceeded
• Frontend dev — build chat UIs without a real API key
• Multi-provider testing — test your abstraction layer against OpenAI, Anthropic, and Google formats

Examples

Quick mock (no format needed)

mock_quick(prompt="Explain quantum computing", length="short")

Test OpenAI integration

mock_openai_chat(
    messages=[{"role": "user", "content": "Hello!"}],
    model="gpt-4o",
    response_type="text"
)

Simulate a rate limit error

mock_simulate_error(provider="anthropic", error_type="rate_limit")

Deterministic response with seed

mock_quick(prompt="Write a haiku", seed=42)

Response Control Headers

All mock tools support:

• length: "short", "medium", "long", "xl", "random"
• response_type: "auto", "text", "code", "json", "markdown", "list"
• error: "none", "rate_limit", "server_error", "timeout", "invalid_key", "context_length", "content_filter"
• delay_ms: 0–5000 — artificial latency
• seed: integer — reproducible responses

Environment Variables

Variable	Description	Default
MOCK_LLM_API_KEY	API key for authenticated access	`` (free tier)
MOCK_LLM_API_URL	Override API base URL	https://mock-llm-api.rebaselabs.online

Part of the RebaseKit Agent Infrastructure Stack

Mock LLM MCP is part of the RebaseKit suite of agent-native APIs:

• WeTask — web extraction & browser automation
• CodeExec — sandboxed code execution
• PII API — detect & mask sensitive data
• DocParse — document parsing & OCR
• DataTransform — data format conversion & querying
• Mock LLM — mock any LLM provider for testing

"The internet was built for humans. RebaseKit makes it work for agents."