list_metadata

Lists available metadata of a given type

{
    "sid"             : "",
    "metadata_type"   : "ApexClass",
    "murl"            : ""
}

execute_apex

Executes a block of Apex

{
    "project_name"    : "my project name"
    "debug_categories": [
        {
            "category": "Apex_code",
            "level": "DEBUG"
        },
        {
            "category": "Apex_profiling",
            "level": "DEBUG"
        }
    ],
    "body"            : "String foo = 'bar';"
}

list of categories supported by MavensMate:

'Db', 'Workflow', 'Validation', 'Callout', 'Apex_code', 'Apex_profiling', 'Visualforce'

list of levels supported by MavensMate:

'None', 'ERROR', 'WARN', 'INFO', 'DEBUG', 'FINE', 'FINER', 'FINEST'