Standardized interfaces such as the Model Context Protocol (MCP) make it easier to connect tools to agents, but connection alone is not orchestration. When many related tools are exposed as a flat callable palette, agents must identify relevant tools, resolve substitutes, pass intermediate outputs, and decide when a workflow is complete. We introduce RealFin, a finance-domain diagnostic benchmark for evaluating workflow construction under MCP-style flat tool exposure. RealFin contains 1524 tasks generated from 108 author-designed financial workflow templates over real market, macroeconomic, and company-data APIs. Each task is paired with an executable reference program that specifies one verified solution path, while the 85 agent-callable tools include explicit alternative, dependency, and related-tool metadata to represent non-unique paths, prerequisite tools, and near-neighbor ambiguity. This design supports path-independent answer scoring together with process-level evaluation of tool selection, ordering, parameter planning, entity grounding, temporal grounding, orchestration success, and error recovery. Across ReAct-style flat exposure, retrieval-based exposure, oracle-controlled variants, and progressive tool disclosure, current agents often achieve nonzero answer accuracy while failing to construct reliable workflows. These results suggest that MCP-style tool connectivity needs structured disclosure and workflow-aware evaluation, especially in finance where temporal constraints and overlapping tools are intrinsic.