IT & Data

Legacy system documentation generation

Generate readable documentation for undocumented legacy systems — data models, integration points, business logic, and dependencies — from source code, database schemas, and configuration.

AugmentationPattern-matchingCost reductionAccuracy

50–70%

reduction in system discovery effort

Opportunity assessment

Business Impact
2

Minor improvement. Small efficiency gain with limited effect on overall turnover or bottom line.

Feasibility
3

Moderate effort. Requires configuration, prompt engineering, and testing. A capable team can get there but expect several months.

Data Readiness
4

Light data requirements. Uses straightforward inputs — documents, product descriptions, customer records — that are usually accessible with minimal prep.

Risk Exposure
4

Low risk. Limited external exposure. A human reviews output before it reaches anyone outside the team.

Change Complexity
5

Very easy to absorb. Runs quietly in the background or gives people a helpful new input. Makes everyday work easier with almost no friction.

Tooling required

Standard LLMRAG system

Things to consider

  • Undocumented legacy systems are the single biggest hidden cost in most replatforming programmes, and the knowledge usually lives with two people who are close to retirement. Capturing it has value even if you never replace the system.

  • The model will describe what the code does, not why it does it. The business rationale for an odd rule still has to come from a person — use the generated documentation as the interview prompt.

  • Treat the output as a draft to be verified, not as fact. A confidently wrong description of a payment routine is more dangerous than a blank page.

  • Experiment starter: Pick one system a replatforming programme depends on. Generate the documentation, then have the two people who know it best mark it up. Time how long the markup takes versus the estimate for documenting from scratch.

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