mcap-mcp-server 0.4.0

A generic SQL query interface for MCAP robotics data via the Model Context Protocol

mcap-mcp-server

Query your robot's MCAP recordings with SQL — straight from your LLM.

Point Claude, Cursor, or any MCP client at your bag files. Ask questions in plain English. Get SQL-powered answers from DuckDB. No scripts, no pipelines, no BS.

MCAP files → mcap-mcp-server → DuckDB (in-memory) → SQL results → LLM

Supports JSON, Protobuf, ROS 1, ROS 2, and FlatBuffers out of the box.

Full documentation

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Install

Requires uv (the Python package runner). If you don't have it:

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

That's it — uvx handles the rest. No pip install needed.

Manual install (optional): pip install mcap-mcp-server[all]

Configure Your MCP Client

Copy-paste the config below. That's it — no API keys, no setup, no database.

Cursor

Add to .cursor/mcp.json in your project:

{
  "mcpServers": {
    "mcap-query": {
      "command": "uvx",
      "args": ["mcap-mcp-server[all]"]
    }
  }
}

Claude Desktop

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "mcap-query": {
      "command": "uvx",
      "args": ["mcap-mcp-server[all]"]
    }
  }
}

Windsurf / VS Code / Other MCP Clients

Same JSON — check your client's docs for where to put it.

Recordings outside the project? Set MCAP_DATA_DIR=/path/to/recordings as an env var, or just give the LLM an absolute path — it handles that too.

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What Can It Do?

Once configured, just talk to your LLM. It has 6 tools:

Tool	What it does
list_recordings	Find MCAP files in your project (or any path)
get_recording_info	Metadata, channels, attachments for a file
get_schema	SQL table names & column types — for query planning
load_recording	Decode MCAP data into DuckDB
query	Run SQL (full DuckDB — including ASOF JOIN)
get_statistics	Quick stats (min/max/mean/std) for numeric fields

Example Prompts

Just ask your LLM:

• "List all my recordings and show me what topics are in session_003.mcap"
• "Load the battery data and find all moments where voltage dropped below 22V"
• "Correlate IMU acceleration with motor current using an ASOF JOIN"
• "Compare average battery voltage across my last 5 runs"

Example SQL (under the hood)

-- Time-windowed stats
SELECT (timestamp_us / 1000000) as second,
       AVG(voltage) as avg_v, MIN(voltage) as min_v
FROM battery GROUP BY second ORDER BY second

-- Cross-sensor correlation via ASOF JOIN
SELECT b.timestamp_us, b.voltage, i.linear_acceleration_x
FROM battery b ASOF JOIN imu i ON b.timestamp_us >= i.timestamp_us

-- Multi-recording comparison
SELECT 'run1' as run, AVG(voltage) FROM r1_battery
UNION ALL
SELECT 'run2', AVG(voltage) FROM r2_battery

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Supported Encodings

Encoding	Install
JSON	Built-in
Protobuf	pip install mcap-mcp-server[protobuf]
ROS 1	pip install mcap-mcp-server[ros1]
ROS 2 (CDR)	pip install mcap-mcp-server[ros2]
FlatBuffers	pip install mcap-mcp-server[flatbuffers]
All	pip install mcap-mcp-server[all]

Configuration (Optional)

Defaults work for most setups. Tune if needed:

Variable	Default	Description
MCAP_DATA_DIR	.	Root directory to scan for MCAP files
MCAP_RECURSIVE	true	Scan subdirectories
MCAP_MAX_MEMORY_MB	2048	Max memory for loaded data (LRU eviction)
MCAP_QUERY_TIMEOUT_S	30	SQL query timeout
MCAP_DEFAULT_ROW_LIMIT	1000	Default result row limit
MCAP_MAX_ROW_LIMIT	10000	Max allowed row limit
MCAP_TRANSPORT	stdio	stdio or sse

Docker

docker run -d \
  -v /data/recordings:/data:ro \
  -e MCAP_DATA_DIR=/data \
  -e MCAP_TRANSPORT=sse \
  -p 8080:8080 \
  ghcr.io/turkenberg/mcap-mcp-server:latest

Development

git clone https://github.com/turkenberg/mcap_mcp_server.git
cd mcap_mcp_server
git submodule update --init
pip install -e ".[dev]"
pytest

License

GNU General Public License v3.0 — see LICENSE.