Self-Hosted Supabase MCP Server

Instructions

Implementation Reference

• src/tools/list_extensions.ts:31-56 (handler)

  The execute function implementing the tool logic: queries pg_extension table for installed extensions (excluding plpgsql), using utilities for SQL execution and response handling.

  execute: async (input: ListExtensionsInput, context: ToolContext) => {
      const client = context.selfhostedClient;
  
      // SQL based on pg_extension
      const listExtensionsSql = `
          SELECT
              pe.extname AS name,
              pn.nspname AS schema,
              pe.extversion AS version,
              pd.description
          FROM
              pg_catalog.pg_extension pe
          LEFT JOIN
              pg_catalog.pg_namespace pn ON pn.oid = pe.extnamespace
          LEFT JOIN
              pg_catalog.pg_description pd ON pd.objoid = pe.oid AND pd.classoid = 'pg_catalog.pg_extension'::regclass
          WHERE
              pe.extname != 'plpgsql' -- Exclude the default plpgsql extension
          ORDER BY
              pe.extname
      `;
  
      const result = await executeSqlWithFallback(client, listExtensionsSql, true);
  
      return handleSqlResponse(result, ListExtensionsOutputSchema);
  },

• src/tools/list_extensions.ts:7-22 (schema)

  Zod schemas defining input (empty), output (array of {name, schema, version, description}), and MCP JSON input schema for the list_extensions tool.

  const ListExtensionsOutputSchema = z.array(z.object({
      name: z.string(),
      schema: z.string(),
      version: z.string(),
      description: z.string().nullable().optional(),
  }));
  
  // Input schema (none needed for this tool)
  const ListExtensionsInputSchema = z.object({});
  type ListExtensionsInput = z.infer<typeof ListExtensionsInputSchema>;
  // Static JSON Schema for MCP capabilities
  const mcpInputSchema = {
      type: 'object', 
      properties: {},
      required: [],
  };

• src/index.ts:101-101 (registration)

  Registers the listExtensionsTool in the availableTools map used by the MCP server.

  [listExtensionsTool.name]: listExtensionsTool as AppTool,