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nemo_07: Such probes are designed for looking at logic or other circuits with moderate or low impedances, not for probing Hi-Q LC tanks. Beside detuning, some of them will introduce measurable damping at 100MHz.
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regenfreak: How you do know? Have you tried? This guy probed the IF output for the residual output of FM front end tuners with multi-stage tuned bandpass filters. He used a Tektronix 500MHz P6202A with input capacitance of 2pF:
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I had a play on a simulator and the BF998 MOSFET probe has the potential to have an effective input Rp that is a couple or orders of magnitude higher than the P6201 at 100MHz. This is partly due to the capacitive divider at the input. However, this can only happen if the MOSFET probe has a snubber at g1 to offset the negative resistance the BF998 will generate here across VHF and well into UHF.
Achieving low input Cp for a useable probe is always going to be a challenge and a lot depends on how small and short (and fragile?) you can make the tip section. This will minimise any capacitance to free space.