Large Language Model (LLM)
// Definition
A neural network trained on massive text datasets to predict the next word in a sequence. Modern LLMs like Claude, GPT-4, and Gemini can answer questions, write code, summarise documents, and follow multi-step instructions — but they don't 'know' anything, they predict plausible continuations from patterns in training data. This is why they sometimes produce confident-sounding falsehoods (hallucinations) and why prompt design matters so much. In QA, LLMs are useful for generating test scaffolding, summarising bug reports, and drafting documentation — but their output always needs human review before it ships.
// Related terms
Hallucination
When an AI model generates output that is fluent, confident, and completely wrong. In QA work this often looks like an LLM inventing a method that doesn't exist on a real API, citing a documentation page that was never written, or producing a test assertion that doesn't actually verify the behaviour described in the prompt. Hallucinations aren't a bug — they're a consequence of how language models work, predicting likely text rather than retrieving facts. The mitigations are: ground the model in real context (paste the actual API spec, not its name), verify generated code by running it, and treat any AI-produced reference (URLs, function names, citations) as untrusted until checked.
Prompt Engineering
The craft of writing inputs to AI tools — language models, chat assistants, coding assistants — so that the output is useful, specific, and aligned with the task. Core principles include being specific about format, providing project context (existing patterns, conventions, examples), asking for chain-of-thought reasoning, enumerating edge cases up front, and iterating across multiple turns rather than expecting a perfect first response.
Model Context Protocol (MCP)
An open standard introduced by Anthropic in late 2024 that lets AI assistants connect to external tools and data sources through a uniform JSON-RPC interface. An MCP server exposes tools (callable functions), resources (readable data), and prompts (templates) to any MCP-compatible host (Claude Desktop, Claude Code, IDE plugins). Build a server once and any compliant client can use it — the protocol is model-agnostic, which makes integrations portable across AI providers.