Agentic AI Reference Architecture

Orchestration · Software component

Direct Tool-Calling Controller

Software componentOrchestrationOrchestration & Toolsarc:DirectToolCallingController

An agent controller that maps a request directly to one or a few structured tool calls without iterative reasoning loops or upfront planning.

Responsibility. Answers simple requests via direct function calls.

Also known as: Direct tool calling, Simple function calling, Structured function-calling agent, OpenAI Functions agent, OPENAI_FUNCTIONS agent, Single tool integration

Variant of Agent Controller abstract

When to choose. Choose for simple, deterministic tasks where a straightforward tool call suffices and latency or budget constraints cannot absorb multi-step reasoning or planning overhead.

specializeswritesinvokesalternative tois configured byinvokesalternative toAgent Controller: specializesAgent ControllerAudit Log Store: writesAudit Log StoreTool Executor: invokesTool ExecutorReAct Agent Controller: alternative toReAct Agent ControllerTool Schema: is configured byTool SchemaNative Function-Calling API: invokesNative Function-Calling …Plan-and-Execute Controller: alternative toPlan-and-Execute Control…
Direct neighbourhood (hover for relationship types)

Relationships

is configured by structural

invokes dependency

writes dependency

alternative to variability

Design guidance

Classification

Patterns
Function calling
Technologies
LangChainOpenAI function calling
Quality attributes
Performance efficiency (ISO/IEC 25010)Cost efficiencyMaintainability (ISO/IEC 25010)Reliability (ISO/IEC 25010 | NIST AI RMF: valid and reliable)Transparency and accountability (NIST AI RMF: accountable and transparent)
Risks mitigated
Unnecessary reasoning overheadNon-deterministic regulated decisionsUnstructured audit trailsTool-call parse errors

Sources

  1. Ch1.2: T. Nguyen, "Core Agent Patterns," in Mastering Agentic AI Systems: Guide for the NVIDIA NCP-AAI Exam, 1st ed. 2026, ch. 1.2. ISBN: 9798244538229.
  2. Ch2.1: T. Nguyen, "Framework Landscape and Selection," in Mastering Agentic AI Systems: Guide for the NVIDIA NCP-AAI Exam, 1st ed. 2026, ch. 2.1. ISBN: 9798244538229.
  3. Ch2.3: T. Nguyen, "LangChain Sequential Frameworks," in Mastering Agentic AI Systems: Guide for the NVIDIA NCP-AAI Exam, 1st ed. 2026, ch. 2.3. ISBN: 9798244538229.
  4. Ch2.6: T. Nguyen, "Tool Integration and Function Calling," in Mastering Agentic AI Systems: Guide for the NVIDIA NCP-AAI Exam, 1st ed. 2026, ch. 2.6. ISBN: 9798244538229.