mcp-servers

Locally-hosted MCP (Model Context Protocol) servers exposed to Claude Code.

Each subdirectory is one MCP server. Registered with Claude via:

claude mcp add-json -s user <name> '{"type":"stdio","command":"<path>","args":[...]}'

Servers

Name	Path	Purpose
forecastlab_db	forecastlab_db/server.py	Read-only SQL access to forecastlab, weewx_db, homeassistant databases

forecastlab_db

Read-only MariaDB facade. Tools: list_databases, list_tables, describe_table, query.

Safety:

• Only the 3 allowlisted databases reachable
• SELECT / SHOW / DESCRIBE / EXPLAIN / WITH only — write statements rejected
• Multi-statement injection rejected
• Hard cap 1000 rows per query (default 200)
• Datetimes serialised as ISO strings

Optional read-only DB user (recommended for production):

CREATE USER 'mcp_ro'@'localhost' IDENTIFIED BY '<secret>';
GRANT SELECT ON forecastlab.* TO 'mcp_ro'@'localhost';
GRANT SELECT ON weewx_db.* TO 'mcp_ro'@'localhost';
GRANT SELECT ON homeassistant.* TO 'mcp_ro'@'localhost';
FLUSH PRIVILEGES;

Then add to ~/.env:

MCP_DB_RO_USER=mcp_ro
MCP_DB_RO_PASSWORD=<secret>

The server prefers these if set; otherwise falls back to DB_USER/DB_PASSWORD.

Adding a new MCP server

1. Create a subdirectory: mcp_servers/<name>/server.py
2. Use the mcp Python SDK and the FastMCP helper (see forecastlab_db/server.py as a template)
3. Register with Claude:

   claude mcp add-json -s user <name> \
     '{"type":"stdio","command":"/home/help4bis/miniconda3/envs/forecastlab/bin/python","args":["/home/help4bis/lib/mcp_servers/<name>/server.py"]}'
   

4. Verify: claude mcp list should show it Connected
5. Commit + push to Gitea

Testing

Each server's stdio-style protocol is best tested by Claude itself. For sanity-check the read-only guard:

/home/help4bis/miniconda3/envs/forecastlab/bin/python -c "
import sys; sys.path.insert(0, '/home/help4bis/lib/mcp_servers/forecastlab_db')
from server import _validate_read_only
_validate_read_only('SELECT 1')        # passes
_validate_read_only('DROP TABLE foo')  # raises ValueError
"