Mr. Bloomberg and Ms. Quinn agreed on Tuesday that the grading system provided diners with more access to information, but some restaurant owners argued that the grading system was far too blunt and was frequently based on relatively minor issues.

“It could be a cracked toilet cover; it could be a gap around a pipe,” said Peter Hansen, the director of operations at Benchmarc Restaurants, which owns several expensive dining establishments in the city.

“But,” Mr. Hansen added, “what your customer is thinking is: old tuna.”

Elizabeth Meltz, who oversees food safety at Mario Batali’s Italian restaurants, said that she supported a grading system and that it could improve public health.

But, echoing other restaurant workers, she said some city health inspectors seemed inconsistent in their standards, asking about certain elements of the kitchen on some visits and not on others. Sometimes, the inspectors appeared unfamiliar with complex dishes like terrine and kimchi, Ms. Meltz said, and on one occasion, she believed that an inspector was disrespectful to her because of her gender.

“There can be a lack of ability to communicate whatever expertise they may or may not have,” Ms. Meltz said. “I’m all for the grading system. If we could help the health department get the inspectors that they need and deserve, it should work for everybody.”

Ms. Meltz said she wished inspectors and restaurant workers better understood each other’s needs. “Inspectors could come in and dine, and see what our food is like, and why our antipasti are at room temperature,” she suggested. “And a couple of our sous chefs could take a week of the inspectors’ courses, to see how they inspect, so it’s not this guessing game.”

In the case of James, which serves artisanal American cuisine on the ground floor of a Prospect Heights brownstone, one of the reasons for its “B” rating was the lack of a ventilating fan in an employee bathroom.