Weights & Biases MCP Server

A Model Context Protocol (MCP) server for querying Weights & Biases Weave traces. This server allows a MCP Client to:

• query W&B Weave traces
• write text and charts to W&B Reports

Available tools

wandb

• query_wandb_gql_tool: Execute an arbitrary GraphQL query against wandb experiment tracking data including Projects, Runs, Artifacts, Sweeps, Reports, etc.

Weave

• query_weave_traces_tool: Queries Weave traces with powerful filtering, sorting, and pagination options. Returns either complete trace data or just metadata to avoid overwhelming the LLM context window.

• count_weave_traces_tool: Efficiently counts Weave traces matching given filters without returning the trace data. Returns both total trace count and root traces count to understand project scope before querying.

Saving Anaysis

• create_wandb_report_tool: Creates a new W&B Report with markdown text and HTML-rendered visualizations. Provides a permanent, shareable document for saving analysis findings and generated charts.

Usage

Ensure you specify the W&B Entity and W&B Project to the LLM/MCP Client.

Example query for Claude Desktop:

how many openai.chat traces in the wandb-applied-ai-team/mcp-tests weave project? plot the most recent 5 traces over time and save to a report

Installation

git clone https://github.com/wandb/mcp-server.git
cd mcp-server && uv venv && source .venv/bin/activate
uv pip install -e .

Configuration

1. Create a .env file in the root directory with your Weights & Biases API key:

WANDB_API_KEY=your_api_key_here

Running the Server

Run the server using:

uv run src/mcp_server/server.py

Client Setup

Claude Desktop

    "mcpServers": {
        "weights_and_biases": {
        "command": "uv",
        "args": [
            "--directory",
            "/ABSOLUTE/PATH/TO/PROJECT",
            "run",
            "src/mcp_server/server.py"
        ]
        }
    }

TODOs

• [ ] Add W&B Models data
• [ ] Convert to run with npx
• [ ] Make more configurable: specify wandb URL
• [ ] Work on reports plots prompt for consistent visualizations
• [ ] Look into auth solutions

Troubleshooting

Error: spawn uv ENOENT

If you encounter an error like this when starting the MCP server:

Error: spawn uv ENOENT

This indicates that the uv package manager cannot be found. Fix this with these steps:

1. Install uv using the official installation script:

   curl -LsSf https://astral.sh/uv/install.sh | sh
   

2. If the error persists after installation, create a symlink to make uv available system-wide:

   sudo ln -s ~/.local/bin/uv /usr/local/bin/uv
   

3. Restart your application or IDE after making these changes.