postgres-mcp

Instructions

Returns:
    List of schemas with name and owner

Implementation Reference

• postgres_mcp/server.py:126-140 (handler)

  MCP tool handler for 'list_schemas': calls PostgresClient.list_schemas() and formats output using SchemaSummary models.

  @mcp.tool()
  @handle_db_error
  def list_schemas() -> dict:
      """List all schemas in the PostgreSQL database.
      
      Returns:
          List of schemas with name and owner
      """
      client = get_client()
      schemas = client.list_schemas()
      
      return {
          "schemas": [SchemaSummary.from_row(s).model_dump() for s in schemas],
      }

• postgres_mcp/postgres_client.py:183-200 (handler)

  Core handler logic in PostgresClient: executes SQL query to fetch schemas from information_schema.schemata, excluding system schemas.

  def list_schemas(self) -> list[dict]:
      """List all schemas in the database.
      
      Returns:
          List of schema dicts with name and owner
      """
      query = """
          SELECT 
              schema_name,
              schema_owner
          FROM information_schema.schemata 
          WHERE schema_name NOT IN ('information_schema', 'pg_catalog', 'pg_toast')
          ORDER BY schema_name
      """
      with self.get_cursor() as cursor:
          cursor.execute(query)
          return [dict(row) for row in cursor.fetchall()]

• postgres_mcp/models.py:17-29 (schema)

  Pydantic model defining the output schema for schemas list, with from_row method to convert database rows.

  class SchemaSummary(BaseModel):
      """Schema info for list responses."""
      
      name: str
      owner: Optional[str] = None
      
      @classmethod
      def from_row(cls, row: dict) -> "SchemaSummary":
          return cls(
              name=row.get("schema_name", ""),
              owner=row.get("schema_owner"),
          )

• postgres_mcp/server.py:126-140 (registration)

  Registration of the 'list_schemas' tool via FastMCP @mcp.tool() decorator.

  @mcp.tool()
  @handle_db_error
  def list_schemas() -> dict:
      """List all schemas in the PostgreSQL database.
      
      Returns:
          List of schemas with name and owner
      """
      client = get_client()
      schemas = client.list_schemas()
      
      return {
          "schemas": [SchemaSummary.from_row(s).model_dump() for s in schemas],
      }