Perceive, Interact, Reason: Building Tool-Augmented Visual Agents for Spatial Reasoning

While recent vision-language models (VLMs) demonstrate strong multimodal understanding, they remain limited in spatial reasoning tasks that require active evidence acquisition and multi-step visual interaction. This limitation suggests that relying solely on implicit visual representations from vision encoders is insufficient for recovering fine-grained spatial evidence. We introduce *PERception-Interaction-reason Agent* (**PERIA**), a tool-augmented visual agent for spatial reasoning tasks across map reasoning, visual probing, and vision reconstruction. **PERIA** uses two lightweight tool families: *vision perception tools* for exposing textual, symbolic, and spatial evidence, and *vision interaction tools* for manipulating visual context, tracing paths, and verifying spatial relations. To train **PERIA**, we develop a unified recipe that combines supervised tool-use trajectory synthesis, composite rewards, and Observation-Relaxed Group-in-Group Policy Optimization (OR-GIGPO) for effective multi-tool behavior. Experiments on 13 benchmarks from 8 datasets show that **PERIA**-8B improves over the Qwen3-8B backbone by 10.0% on in-distribution benchmarks and 4.4% on out-of-distribution benchmarks, while outperforming previous state-of-the-art baselines of similar size by 7.0%–14.8%. It also achieves performance comparable to much larger models such as Qwen3-VL-235B-A22B-Thinking and GPT-5, demonstrating the effectiveness of **PERIA** in enhancing spatial reasoning capabilities.