Product Specification

Role

The product specification is the highest-level practical description of intended product behavior.

It should answer questions such as:

• why the product exists
• who it is for
• which workflows are first-class
• what must work even under failure conditions
• what is explicitly out of scope
• what acceptance criteria define a meaningful demo or release

What belongs in a product specification

Typical specification content includes:

• product purpose
• core philosophy
• domain model
• workflow definitions
• privacy and security expectations
• non-goals
• implementation sequence guidance where it affects scope or delivery order
• acceptance criteria

The spec should focus on product truth, not every local implementation detail.

What usually does not belong there

These items often belong elsewhere unless they directly affect product commitments:

• temporary repository conventions
• local tooling setup
• narrow UI polish decisions
• one-off debugging guidance
• editorial or publishing mechanics that do not change the product model

Why it matters in AI-assisted work

AI can generate plausible implementation very quickly. Without a clear product specification, that implementation may optimize for convenience instead of intent.

The specification gives reviewers and contributors a stable standard for deciding whether generated output still belongs to the intended product.

Let Books context

In Let Books, AGENTS.md is the core product specification.

It defines:

• project purpose
• domain and workflow model
• multi-tenant and localization direction
• manual workflow and AI-optional principles
• acceptance criteria for the first demo

That makes it more than an overview. It is the main product authority in the repository.