describe_table
Retrieve PostgreSQL table structure including columns, data types, and constraints to understand database schema and plan queries effectively.
Instructions
Get table structure
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| table | Yes | Table name | |
| schema | No | Schema name (default: public) |
Implementation Reference
- src/index.ts:447-510 (handler)Main handler function for 'describe_table' tool. Validates input, queries PostgreSQL information_schema for table columns, data types, nullability, defaults, primary key status, and max length. Returns JSON-formatted results.
private async handleDescribeTable(args: any) { await this.ensureConnection(); if (!args.table) { throw new McpError(ErrorCode.InvalidParams, 'Table name is required'); } const schema = args.schema || 'public'; try { const result = await this.client!.query(` SELECT c.column_name, c.data_type, c.is_nullable, c.column_default, CASE WHEN pk.constraint_type = 'PRIMARY KEY' THEN true ELSE false END AS is_primary_key, c.character_maximum_length FROM information_schema.columns c LEFT JOIN ( SELECT tc.constraint_type, kcu.column_name, kcu.table_name, kcu.table_schema FROM information_schema.table_constraints tc JOIN information_schema.key_column_usage kcu ON tc.constraint_name = kcu.constraint_name WHERE tc.constraint_type = 'PRIMARY KEY' ) pk ON c.column_name = pk.column_name AND c.table_name = pk.table_name AND c.table_schema = pk.table_schema WHERE c.table_schema = $1 AND c.table_name = $2 ORDER BY c.ordinal_position `, [schema, args.table]); return { content: [ { type: 'text', text: JSON.stringify(result.rows, null, 2), }, ], }; } catch (error) { throw new McpError( ErrorCode.InternalError, `Failed to describe table: ${getErrorMessage(error)}` ); } } - src/index.ts:234-251 (schema)Input schema definition for the 'describe_table' tool, specifying required 'table' parameter and optional 'schema'.
{ name: 'describe_table', description: 'Get table structure', inputSchema: { type: 'object', properties: { table: { type: 'string', description: 'Table name', }, schema: { type: 'string', description: 'Schema name (default: public)', }, }, required: ['table'], }, }, - src/index.ts:267-268 (registration)Dispatch/registration case in the tool request handler switch statement that routes 'describe_table' calls to the handleDescribeTable function.
case 'describe_table': return await this.handleDescribeTable(request.params.arguments); - src/index.ts:137-253 (registration)Tool list registration in ListToolsRequestSchema handler, including 'describe_table' with its schema.
this.server.setRequestHandler(ListToolsRequestSchema, async () => ({ tools: [ { name: 'connect_db', description: 'Connect to PostgreSQL database. NOTE: Default connection exists - only use when requested or if other commands fail', inputSchema: { type: 'object', properties: { host: { type: 'string', description: 'Database host', }, port: { type: 'number', description: 'Database port (default: 5432)', }, user: { type: 'string', description: 'Database user', }, password: { type: 'string', description: 'Database password', }, database: { type: 'string', description: 'Database name', }, }, required: ['host', 'user', 'password', 'database'], }, }, { name: 'query', description: 'Execute a SELECT query', inputSchema: { type: 'object', properties: { sql: { type: 'string', description: 'SQL SELECT query (use $1, $2, etc. for parameters)', }, params: { type: 'array', items: { type: ['string', 'number', 'boolean', 'null'], }, description: 'Query parameters (optional)', }, }, required: ['sql'], }, }, { name: 'execute', description: 'Execute an INSERT, UPDATE, or DELETE query', inputSchema: { type: 'object', properties: { sql: { type: 'string', description: 'SQL query (INSERT, UPDATE, DELETE) (use $1, $2, etc. for parameters)', }, params: { type: 'array', items: { type: ['string', 'number', 'boolean', 'null'], }, description: 'Query parameters (optional)', }, }, required: ['sql'], }, }, { name: 'list_schemas', description: 'List all schemas in the database', inputSchema: { type: 'object', properties: {}, required: [], }, }, { name: 'list_tables', description: 'List tables in the database', inputSchema: { type: 'object', properties: { schema: { type: 'string', description: 'Schema name (default: public)', }, }, required: [], }, }, { name: 'describe_table', description: 'Get table structure', inputSchema: { type: 'object', properties: { table: { type: 'string', description: 'Table name', }, schema: { type: 'string', description: 'Schema name (default: public)', }, }, required: ['table'], }, }, ], }));