
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Given the function $f(x)=x- \frac {a}{x}-(a+1)\ln x$ $(a\in\mathbb{R})$.
- (I) When $a= \frac {1}{2}$, find the intervals of monotonicity for the function $f(x)$.
- (II) Determine whether there exists a real number $a$ such that $f(x)\leqslant x$ always holds. If it exists, find the range of values for $a$; if not, explain why.

Present the answer in LaTex format: \boxed{Your answer}
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