The administrator of the Agency for International Development, M. Peter McPherson, was for weeks the only official Reagan appointee at the agency, but last week he was joined by an official general counsel, and this week AID got a new official spokesman.

Unofficially, several persons have been filling desks at the agency, which is a primary conduit for the distribution of nonmilitary foreign aid, and a spate of nominations are expected to be announced shortly.

Sworn in last week as general counsel was John R. Bolton, formerly of the Washington law firm of Convington & Burling, and the new director of public affairs is Herb Harmon.

Unannounced but reportedly already on the job as assistant administrator for legislative affairs is Jack Murphy, former administrative aide to Sen. Barry Goldwater (R-Ariz.), and at her desk as his deputy is Mimi Laxalt, a transition worker and daughter of Reagan insider Sen. Paul Laxalt (R-Nev.).

Not officially on the job but attending briefings is Samuel Martinez, who is in line for the post of assistant administrator for Latin America and the Caribbean. Martinez was with the Community Services Administration in the Nixon administration and its director in the Ford administration.

Thomas Rollin, another old hand at CSA, is the expected choice for assistant administrator for program and policy coordination, and Jon D. Holstine, a minority staff member of the House Foreign Affairs Committee, is expected to be named assistant administrator for Asia. Herbert L. Beckington is expected to stay on in the job of auditor general.

That leaves the deputy administrator's spot still to be filled, as well as several assistant administrator jobs -- including those for Africa and the Near East.