ONE OF the biggest recent development projects proposed for the Washington suburbs — MGM Resorts International’s $925 million casino complex at National Harbor — received final approval for construction Monday from the Prince George’s County Council. A jackpot of promises made by the company — to generate revenue, jobs, contracts and charity — had the desired effect. Even on the querulous council, opposition to this behemoth near the banks of the Potomac ranged from muted to inaudible.

Here’s hoping that MGM makes good on its promises because they would, in fact, provide an economic shot in the arm to the county. Even those who opposed planting a casino with 3,600 slot machines and 140 gaming tables scarcely 10 miles south of the Capitol, as we did, would be gratified if the payoff provides the promised material benefits for the state and county.

So far, that payoff remains prospective. After extensive negotiations, MGM and county officials unveiled an agreement last month under which the company pledged its “best efforts” to ensure that the county and its residents enjoy the fruits of the anticipated windfall of construction contracts and jobs, as well as permanent employment once the project is complete (in 2016 if all goes as planned).

The term “best efforts” — defined in fine legalese and bargained over at length — is not a binding obligation. But it is a public expression of commitment, and MGM officials will be aware that the public is watching.

The company pledged that 40 percent of its 3,800 employees at National Harbor will be county residents when the project opens, rising to 50 percent by the fifth year of operations. MGM also said that at least 20 percent of the construction jobs at the site will go to county residents (with an “aspirational goal” of 30 percent) and that, once the resort is up and running, a similar proportion of the contracts it awards will go to minority-owned businesses in the county.

A view of the planned MGM casino at National Harbor

If the company is judged not to have made “best efforts” to hit those benchmarks (as determined by a compliance council consisting mainly of county-appointed monitors), it may face fines. Its real incentive is reputational; other localities where MGM may propose projects will note how the company performs in Prince George’s.

The potential benefits for the county go beyond the projected $40 million to $45 million in tax revenue (plus more for nonprofits and workforce training) that Prince George’s expects to rake in from the MGM project, which includes a large hotel, glitzy restaurants and a theater. With other major development projects in the county’s pipeline — including, possibly, the new headquarters for the FBI — MGM could help develop and nurture local contractors, contributing to a more vibrant private sector. That would be critical for a county that, despite enormous strides, remains the economic laggard among Washington’s close-in suburban localities.