From need to generative specification · Lesson 2

Generation, context and knowledge limits

7 min read

Lesson objectives

  • Diagnose generation errors by distinguishing missing input, truncation and unsupported inference, and choose a test that exposes each cause.

A coherent model response can make us forget that coherence is not a source check. A language model handles text units called tokens and learns relationships that help it produce a sequence suitable for its context. A token is not necessarily a word: depending on the tokenizer, it may represent part of a word, punctuation or another unit. Therefore a single fixed words-to-tokens multiplier is unsuitable across Arabic, English and all models. For a long task, use the model's tokenizer or available usage information rather than judging capacity only from page count. A specialist need not memorize tokenization algorithms to understand their operational consequences.

Separate three sources of apparent knowledge: information learned during training, material supplied in the current request, and information fetched by an external tool during processing. Training does not provide a guaranteed ledger of every fact or establish its currency. Current input can be inspected if an appropriately permitted record is retained. Tool results need their own source and date checks. Mentioning a filename does not mean its contents were sent, and writing a URL does not prove that the system opened it. If an answer depends on a new price table, first establish that the correct table reached the step generating the answer.

The context window limits the material a system can process for a request under its design. Accounting rules vary and may include instructions, conversation history, tool results and the material to be summarized. Do not put a universal capacity number in a task card. Instead, require measurement of the actual input and an output allowance appropriate to the chosen system's documentation. When an input exceeds a limit, an application might reject it, truncate it or summarize portions. Do not assume which behavior occurs without inspecting its settings and records. The original file containing a final page does not prove that the model received that page's text.

Receiving all the text still does not prove that the system uses every part effectively. The study “Lost in the Middle” found position-related performance differences for particular models and tasks. Its findings are not a universal failure rate for every current model. Use them as a reason to test evidence placement in your own task. Place decisive information near the beginning, middle and end of synthetic inputs while keeping other conditions comparable. Check whether each output preserves it. Failure identifies a defect in the tested setup; success does not guarantee performance for every length, format or language. The useful outcome is a documented observation with a defined scope.

Unsupported generation may appear as a nonexistent product name, a precise-looking number or a causal explanation inferred merely from two events occurring together. NIST's generative-AI profile discusses confidently presented false content as confabulation. In practice, tone should not determine whether a statement is accepted as true. Asking the system to “be certain” does not supply evidence. Asking for a confidence percentage does not make that number statistically calibrated; that would need an appropriate evaluation. Requesting an explicit unknown value can help define desired behavior, but compliance with the request still needs testing.

When an error appears, begin with a narrow question: was the necessary information present in the actual input? If not, inspect input collection or task scope. If it existed in the file but never reached the request, inspect extraction and truncation. If it reached the request but the output ignored it, inspect instructions, placement, contradictions and context handling. If the evidence was used but arithmetic was wrong, isolate the calculation and use a reliable calculation tool where available. Replacing the whole prompt at once obscures the cause. A useful experiment changes an identifiable factor and compares its effect on a case whose expected answer was established beforehand.

Repetition serves two different purposes. Repeating an unchanged request may reveal instability, but it cannot supply missing information. Repeating a request after repairing an incomplete input tests a specific repair. Record attempt counts and do not present only the best result as typical behavior. If three attempts give two different dates, inspect the original evidence instead of voting between answers. A repeated date is still unsupported when the source never states it. If the tool exposes settings that affect generation diversity, record them. Reducing diversity does not itself prevent semantic error or guarantee identical outputs in every environment.

Conversation memory also differs from project state. A user may still see earlier messages in the interface while a new request no longer contains every message in its original form. Send decisive requirements from an explicit state record rather than relying on a system to recall an exception mentioned hours ago. A useful record contains the input version, governing rule, completed work and unresolved issues. It supports continuation and review without necessarily storing all sensitive content. Retain the smallest amount of information that permits diagnosis under the organization's policy, and ensure the record is actually available at the next step.

Images and audio present related limits through different input channels. A table image may contain difficult-to-read figures; a transcript may omit a negation. A fluent generated description does not establish the number's accuracy. The transferable principle is to inspect the transformation before generation and then inspect the inference. This program uses text-based practice with explicit inputs and clear limits on what is being tested. A real image or audio application needs cases designed for those modalities. Successful text examples cannot alone establish its accuracy. Before expanding scope, identify which new failure paths the additional input channel creates and how each will be observed.

Lesson summary

Diagnose what actually reached the model, then inspect evidence use, inference and calculation; confidence in wording does not establish truth.