A Legal Prompt Library is a curated collection of natural-language instructions (prompts) specifically designed to guide legal AI tools through their tasks. The ABA (American Bar Association) defines it as "the natural evolution of the form book in the age of AI". In 2025, 58% of US law firms had adopted AI in their day-to-day workflows, making structured prompting essential.
A Legal Prompt Library typically covers several categories of use: legal research ("Analyse recent case law on..."), drafting ("Draft a non-compete clause compliant with..."), risk analysis ("Identify the problematic clauses in this contract...") and litigation preparation ("Summarise the arguments in favour of..."). Prompt chaining — the structured sequencing of several prompts — makes it possible to handle complex analyses step by step.
For law firms, building an internal Legal Prompt Library is a strategic investment: it captures collective know-how, ensures the consistency of AI outputs and accelerates the onboarding of new team members. Pseudonymisation of data is mandatory before any submission to an AI model, and every prompt should be tested and validated by a qualified lawyer before being added to the library.