Reinforcement learning (RL) and sim-to-real transfer have advanced robotic manipulation of rigid objects. Yet, policies remain brittle when applied to articulated mechanisms due to contact-rich dynamics and under-modeled joint phenomena such as friction, stiction, backlash, and clearances. We address this challenge through dexterous in-hand manipulation of articulated tools using a robotic hand with reduced articulation and kinematic redundancy relative to the human hand. Our controller augments a simulation-trained base policy with a sensor-driven refinement learned from hardware demonstrations, conditioning on proprioception and target articulation states while fusing whole-hand tactile and force feedback with the policy's internal action intent via cross-attention-based integration. This design enables online adaptation to instance-specific articulation properties, stabilizes contact interactions, regulates internal forces, and coordinates coupled-link motion under perturbations. We validate our approach across a diversity of real-world examples, including scissors, pliers, minimally invasive surgical tools, and staplers. We achieve robust transfer from simulation to hardware, improved disturbance resilience, and generalization to previously unseen articulated tools, thereby reducing reliance on precise physical modeling in contact-rich settings.

Manipulating articulated tools, such as tweezers or scissors, has rarely been explored in previous research. Unlike rigid tools, articulated tools change their shape dynamically, creating unique challenges for dexterous robotic hands. In this work, we present a hierarchical, goal-conditioned reinforcement learning (GCRL) framework to improve the manipulation capabilities of anthropomorphic robotic hands using articulated tools. Our framework comprises two policy layers: (1) a low-level policy that enables the dexterous hand to manipulate the tool into various configurations for objects of different sizes, and (2) a high-level policy that defines the tool's goal state and controls the robotic arm for object-picking tasks. We employ an encoder, trained on synthetic pointclouds, to estimate the tool's affordance states--specifically, how different tool configurations (e.g., tweezer opening angles) enable grasping of objects of varying sizes--from input point clouds, thereby enabling precise tool manipulation. We also utilize a privilege-informed heuristic policy to generate replay buffer, improving the training efficiency of the high-level policy. We validate our approach through real-world experiments, showing that the robot can effectively manipulate a tweezer-like tool to grasp objects of diverse shapes and sizes with a 70.8 % success rate. This study highlights the potential of RL to advance dexterous robotic manipulation of articulated tools.