The vocabulary of the directory, defined plainly. Every entry on Hyland links back to these concepts — and every definition is written to be quoted.
AI Agent
A software system that uses a large language model to pursue a goal autonomously: it plans steps, calls tools (APIs, code execution, web search), observes results, and iterates — instead of answering a single prompt. Frameworks like LangGraph, AutoGen, and CrewAI provide the scaffolding for building agents.
Multi-Agent System
An architecture where several AI agents with distinct roles (planner, coder, reviewer) collaborate on a task, passing messages and delegating subtasks. Useful when a problem decomposes into specialties, at the cost of orchestration complexity.
Hyland Score
A 1–100 quality ranking computed by Hyland.ai for every directory entry. For GitHub repositories it is fully deterministic — computed from public signals: stars (30%), forks (15%), commit velocity (20%), documentation (15%), community (10%), and freshness (10%). For platforms and agent frameworks it blends community traction, feature completeness, documentation quality, and editorial weighting.
Open Weights
A model whose trained parameters are published for anyone to download, run, and often fine-tune — e.g. Llama, DeepSeek, Qwen. Distinct from "open source" in the strict sense: training data and code may remain closed, and usage is governed by the model license.
Self-Hostable
Software you can run on your own infrastructure rather than the vendor's cloud. For AI, this means your prompts and data never leave your machines — a hard requirement in regulated industries and the main reason open-weights models matter.
Context Window
The maximum amount of text (measured in tokens) a model can consider at once — your prompt plus its working memory. Larger windows (128K–1M tokens) enable whole-codebase analysis and long-document reasoning; smaller ones are cheaper and faster.
RAG (Retrieval-Augmented Generation)
A pattern where the model retrieves relevant documents from a knowledge base (usually via a vector database) before answering, grounding responses in your private data instead of relying on training memory. The standard approach for enterprise chatbots.
MoE (Mixture of Experts)
A model architecture that activates only a fraction of its total parameters per token — e.g. 37B active out of 671B total. Delivers large-model quality at small-model inference cost; used by DeepSeek, Qwen3, Llama 4, and Kimi K2.
Fine-Tuning
Further training a pre-trained model on your own data to specialize its behavior, tone, or domain knowledge. Parameter-efficient methods (LoRA, QLoRA) make this possible on a single GPU for open models.
Function Calling / Tool Use
A model's ability to emit structured requests to external tools — search, calculators, APIs, databases — and incorporate the results. The primitive that makes agents possible.
LLM (Large Language Model)
A neural network trained on massive text corpora to predict and generate language. The engine inside chatbots, agents, and most AI tools — GPT-4o, Claude, Llama, and DeepSeek are all LLMs.
Prompt Engineering
The practice of structuring inputs to get reliably better outputs from a model — role assignment, constraints, examples, and step-by-step instructions. The cheapest performance upgrade available.
Hallucination
When a model generates plausible-sounding but false information — invented facts, citations, or code that doesn't exist. The central reliability problem; mitigated by grounding, retrieval, and verification.
Inference
Running a trained model to produce outputs — as opposed to training it. Inference cost and latency determine what a model costs to serve, which is why smaller efficient models matter.
Latency
The time between sending a request and receiving the first token of the response. Critical for chat, voice, and coding assistants — a model that's smart but slow loses to one that's good and instant.
Token
The unit models read and write — roughly ¾ of an English word. Pricing, context windows, and rate limits are all denominated in tokens.
Embedding
A numeric vector representation of text that captures meaning, so similar texts land close together. The foundation of semantic search and RAG pipelines.
Vector Database
A database optimized for storing embeddings and finding the nearest neighbors of a query vector. The retrieval layer in most RAG systems — Pinecone, Weaviate, pgvector, Qdrant.
Guardrails
Constraints layered around a model to keep outputs safe, on-topic, or correctly formatted — input filters, output validators, refusal policies. What separates a demo agent from a production one.
Human-in-the-Loop (HITL)
A design pattern where an agent pauses for human approval at defined checkpoints — before spending money, sending messages, or executing irreversible actions. The standard for trustworthy automation.
Agentic Workflow
A task executed by a model that plans, uses tools, checks its own results, and iterates — rather than answering in a single pass. The shift from "chatbot" to "coworker".
System Prompt
The standing instruction set that defines a model's role, scope, and behavior before any user message. The single highest-leverage control point in any AI application.
Distillation
Training a smaller model to imitate a larger one's outputs, keeping most of the capability at a fraction of the cost. How many efficient "small" frontier models are made.
Quantization
Compressing a model's weights from 16-bit to 8/4-bit precision so it runs on cheaper hardware with minor quality loss. What makes 70B models runnable on a single GPU.
Multimodal
A model that handles more than one data type — text plus images, audio, or video — in a single system. Enables tasks like "describe this screenshot" or "transcribe and summarize this call".