Kevin Docherty, 28, and 27-year-old John McDonald escaped with more than £400 from the Coral shop in Newlands.
During the raid in January, staff were threatened with the knife and believed the concealed umbrella was a gun.
Docherty and McDonald, who were on licence at the time, were remanded in custody at the High Court in Glasgow pending sentence in June.
The court heard how the pair were caught shortly after the robbery in a nearby newsagents.
They later pleaded guilty to charges of assault and robbery
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