Show HN: LMM for LLMs – A mental model for building LLM apps
by honorable_judge | 2025-04-22 19:32:26+00:00
I've been building agentic apps for some large Fortune 500 companies (T-Mobile, Twilio, etc.) and developed a mental model that serves as a practical guide in building agentic apps: separate the high-level agent specific logic from low-level platform capabilities. I call it the L-MM: the Logical Mental Model for LLM applications.

This mental model has not only been tremendously helpful in building agents but also helping customers think about the development process - so when I am done with a consulting engagement they can move faster across the stack and enable engineers and platform teams to work concurrently without interference, boosting productivity.

So what is the high-level logic vs. the low-level platform work?

High-Level Logic (Agent & Task Specific)

Tools and Environment - These are specific integrations and capabilities that allow agents to interact with external systems or APIs to perform real-world tasks. Examples include:

Booking a table via OpenTable API Scheduling calendar events via Google Calendar or Microsoft Outlook Retrieving and updating data from CRM platforms like Salesforce Utilizing payment gateways to complete transactions

Role and Instructions - Clearly defining an agent's persona, responsibilities, and explicit instructions is essential for predictable and coherent behavior. This includes:

The "personality" of the agent (e.g., professional assistant) Explicit boundaries around task completion ("done criteria") Behavioral guidelines for handling unexpected inputs or situations

Low-Level Logic (Common Platform Capabilities)

Routing - Efficiently coordinating tasks between multiple specialized agents, ensuring seamless hand-offs and effective delegation:

Implementing intelligent load balancing and dynamic agent selection based on task context Supporting retries, failover strategies, and fallback mechanisms

Guardrails - Centralized mechanisms to safeguard interactions and ensure reliability and safety:

Filtering or moderating sensitive or harmful content Real-time compliance checks for industry-specific regulations (e.g., GDPR, HIPAA) Threshold-based alerts and automated corrective actions to prevent misuse

Access to LLMs - Providing robust and centralized access to multiple LLMs ensures high availability and scalability:

Implementing smart retry logic with exponential backoff Centralized rate limiting and quota management to optimize usage Handling diverse LLM backends transparently (OpenAI, Cohere, local open-source models, etc.)

Observability - Comprehensive visibility into system performance and interactions using industry-standard practices: W3C Trace Context compatible distributed tracing for clear visibility across requests Detailed logging and metrics collection (latency, throughput, error rates, token usage) Easy integration with popular observability platforms like Grafana, Prometheus, Datadog, and OpenTelemetry

Why This Matters

By adopting this structured mental model, teams can achieve clear separation of concerns, improving collaboration, reducing complexity, and accelerating the development of scalable, reliable, and safe agentic applications.

I'm actively working on addressing challenges in this domain. If you're navigating similar problems or have insights to share, let's discuss further - i'll leave some links about the stack too if folks want it.

High-level framework - https://openai.github.io/openai-agents-python/ Low-level infrastructure - https://github.com/katanemo/archgw