add_relationship
Add a relationship (foreign key) between two tables with optional cardinality and constraint rules
LABSCO SUMMARY
The diagram on screen changes as you describe it.
Because it drives the drawdb tab you already have open, you watch the schema take shape instead of reading a text description of it — and get_issues plus export_sql mean the same session ends with validated DDL. The browser tab is the server's other half; nothing happens while drawdb is closed.
What it is
A bridge between your assistant and a drawdb diagram open in the browser. The command starts a local WebSocket relay, drawdb finds it, and the diagram becomes readable and writable.
What you get
- The full diagram: tables with fields, canvas layout, relationships and target database type
- Tables listed, added, renamed, recoloured and deleted, with fields added, dropped or altered
- Foreign keys added and removed, with cardinality and constraint rules
- Tables repositioned on the canvas
- The target database switched between MySQL, PostgreSQL, SQLite, MariaDB, T-SQL, Oracle and generic
- Validation issues surfaced: duplicate names, missing primary keys, empty tables, type mismatches
- DDL generated for the target database, with columns, constraints and foreign keys
- The diagram cleared, and the last action on the undo stack inspected
- A connection test against the browser session
Requirements
Node.js 18 or newer and npx. drawdb has to be open in your browser — it scans for the relay on startup and shows a green MCP dot in its header once it has found one.
Setup effort
One command — npx mcp-drawdb
USE CASES
01
Sketching a schema from a description
Tables and foreign keys appear on the canvas as you talk through the model, laid out where you want them.
02
Changing a model you already drew
Rename a table, alter a field's properties, drop a relationship — without hunting for the control in the UI.
03
Checking the model before you build on it
Validation flags duplicate names, missing primary keys and type mismatches while the diagram is still cheap to change.
04
Getting migration SQL out of the picture
Set the target engine, then export DDL with constraints and foreign keys already correct for that dialect.
05
Reading back what is actually on the canvas
The full diagram including layout, so the assistant works from the current state rather than from what it drew earlier.
06
Confirming it is talking to the right tab
One call tells you whether the browser session is connected, before a change silently goes nowhere.
14 tools
Counted once with only startup setup. Other versions, modes or optional credentials may expose a different list.
add_table
Add a new table to the diagram
clear_diagram
Clear all tables and relationships from the diagram. Use with caution.
delete_relationship
Delete a relationship between two tables
delete_table
Delete a table from the diagram. Cascades to remove all relationships involving this table.
export_sql
Generate DDL SQL for the target database. Returns CREATE TABLE statements with columns, constraints, and foreign keys. Note: requires database to be set to a specific type (not 'generic').
get_diagram
Get full overview of the diagram: tables with fields, layout (x/y/width/height), relationships, database type
get_issues
Get validation issues/problems in the current diagram. Checks for: duplicate names, missing primary keys, empty fields, type mismatches, circular dependencies, and more. Call this after making changes to verify the diagram is valid.
list_tables
List all tables in the current drawdb diagram
ping
Test connection to the drawdb browser session
set_database
Set the target database type. This affects available field types, SQL generation, and validation. Options: mysql, postgresql, sqlite, mariadb, transactsql, oraclesql, generic.
set_layout
Set positions of tables on the canvas. Pass an array of {table_name, x, y} to reposition tables. For duplicate table names, pass entries in order.
undo
View the last action on the undo stack. Returns a description of what would be undone. Note: full undo requires UI interaction.
update_table
Update a table: rename, change comment/color, add/drop/alter fields with full property control (unique, unsigned, check, increment, etc.)
BEFORE YOU INSTALL
What to know first
Tools you get
14 tools when we connected.
Requires
- npx on PATH
- Node.js >= 18
CONTEXT COST
Light Standing cost
Rated by the size of the 14 tool definitions that ride along on every turn, not by how many there are
INSTALLATION
Connect your client
Add the block to your client, or run the command directly.
Server setup
Configuration file
JSON
{
"mcpServers": {
"mcp-drawdb": {
"command": "npx",
"args": [
"mcp-drawdb"
]
}
}
}npx
TERMINAL
npx mcp-drawdb
