spanner-list-tables Tool

A “spanner-list-tables” tool retrieves schema information about tables in a Google Cloud Spanner database.

  3 minute read  

About

A spanner-list-tables tool retrieves comprehensive schema information about tables in a Cloud Spanner database. It automatically adapts to the database dialect (GoogleSQL or PostgreSQL) and returns detailed metadata including columns, constraints, and indexes.

This tool is read-only and executes pre-defined SQL queries against the INFORMATION_SCHEMA tables to gather metadata. The tool automatically detects the database dialect from the source configuration and uses the appropriate SQL syntax.

Features

  • Automatic Dialect Detection: Adapts queries based on whether the database uses GoogleSQL or PostgreSQL dialect
  • Comprehensive Schema Information: Returns columns, data types, constraints, indexes, and table relationships
  • Flexible Filtering: Can list all tables or filter by specific table names
  • Output Format Options: Choose between simple (table names only) or detailed (full schema information) output

Use Cases

  1. Database Documentation: Generate comprehensive documentation of your database schema
  2. Schema Validation: Verify that expected tables and columns exist
  3. Migration Planning: Understand the current schema before making changes
  4. Development Tools: Build tools that need to understand database structure
  5. Audit and Compliance: Track schema changes and ensure compliance with data governance policies

Compatible Sources

This tool can be used with the following database sources:

Source Name
Spanner Source

Parameters

The tool accepts two optional parameters:

parametertypedefaultdescription
table_namesstring""Comma-separated list of table names to filter. If empty, lists all tables in user-accessible schemas
output_formatstring“detailed”Output format: “simple” returns only table names, “detailed” returns full schema information

Example

Basic Usage - List All Tables

kind: sources
name: my-spanner-db
type: spanner
project: ${SPANNER_PROJECT}
instance: ${SPANNER_INSTANCE}
database: ${SPANNER_DATABASE}
dialect: googlesql  # or postgresql
---
kind: tools
name: list_all_tables
type: spanner-list-tables
source: my-spanner-db
description: Lists all tables with their complete schema information

List Specific Tables

kind: tools
name: list_specific_tables
type: spanner-list-tables
source: my-spanner-db
description: |
  Lists schema information for specific tables.
  Example usage:
  {
    "table_names": "users,orders,products",
    "output_format": "detailed"
  }

Output Format

Simple Format

When output_format is set to “simple”, the tool returns a minimal JSON structure:

[
  {
    "schema_name": "public",
    "object_name": "users",
    "object_details": {
      "name": "users"
    }
  },
  {
    "schema_name": "public",
    "object_name": "orders",
    "object_details": {
      "name": "orders"
    }
  }
]

Detailed Format

When output_format is set to “detailed” (default), the tool returns comprehensive schema information:

[
  {
    "schema_name": "public",
    "object_name": "users",
    "object_details": {
      "schema_name": "public",
      "object_name": "users",
      "object_type": "BASE TABLE",
      "columns": [
        {
          "column_name": "id",
          "data_type": "INT64",
          "ordinal_position": 1,
          "is_not_nullable": true,
          "column_default": null
        },
        {
          "column_name": "email",
          "data_type": "STRING(255)",
          "ordinal_position": 2,
          "is_not_nullable": true,
          "column_default": null
        }
      ],
      "constraints": [
        {
          "constraint_name": "PK_users",
          "constraint_type": "PRIMARY KEY",
          "constraint_definition": "PRIMARY KEY (id)",
          "constraint_columns": [
            "id"
          ],
          "foreign_key_referenced_table": null,
          "foreign_key_referenced_columns": []
        }
      ],
      "indexes": [
        {
          "index_name": "idx_users_email",
          "index_type": "INDEX",
          "is_unique": true,
          "is_null_filtered": false,
          "interleaved_in_table": null,
          "index_key_columns": [
            {
              "column_name": "email",
              "ordering": "ASC"
            }
          ],
          "storing_columns": []
        }
      ]
    }
  }
]

Reference

fieldtyperequireddescription
typestringtrueMust be “spanner-list-tables”
sourcestringtrueName of the Spanner source to query
descriptionstringfalseDescription of the tool that is passed to the LLM
authRequiredstring[]falseList of auth services required to invoke this tool

Advanced Usage

Example with Agent Integration

kind: sources
name: spanner-db
type: spanner
project: my-project
instance: my-instance
database: my-database
dialect: googlesql
---
kind: tools
name: schema_inspector
type: spanner-list-tables
source: spanner-db
description: |
  Use this tool to inspect database schema information.
  You can:
  - List all tables by leaving table_names empty
  - Get specific table schemas by providing comma-separated table names
  - Choose between simple (names only) or detailed (full schema) output

  Examples:
  1. List all tables with details: {"output_format": "detailed"}
  2. Get specific tables: {"table_names": "users,orders", "output_format": "detailed"}
  3. Just get table names: {"output_format": "simple"}

Additional Resources

  • This tool is read-only and does not modify any data
  • The tool automatically handles both GoogleSQL and PostgreSQL dialects
  • Large databases with many tables may take longer to query


Last modified March 12, 2026: docs: Add page standardization to external tool integrations (#2668) (7679d0a46a9)