Skip to main content

FDD Cursor Rules

· 2 min read
Max Kaido
Max Kaido
Architect

below 4 core action-rules for cursor to make FDD flow smoothly

🔧 Cursor Rule #1: code → FDD​

Rule Name: postfactum-fdd-for-implementation

Trigger: When a module or feature is already implemented and a Feature-Driven Document (FDD) needs to be created.

Action: Generate an FDD that serves as a compressed context snapshot. Avoid architectural evangelism or commentary. This FDD is not for onboarding, it's a memory prosthetic for the author.

Cursor Guidelines:

  • Do not rephrase variable names, keep them 1:1.
  • Skip general explanations unless they clarify implicit design decisions.
  • Capture:
    • Input/output contracts
    • Core logic
    • Dependencies (internal/external)
    • Known limitations or future hooks
  • Avoid:
    • Code style tips
    • Naming suggestions
    • Assumptions about intended audience

Tone: Technical, compressed, no fluff. This is a tool for Max’s brain, not a presentation deck.

⚙️ Cursor Rule #2: FDD → code​

Rule Name: fdd-implementation-tracker

Trigger: When a Feature-Driven Document already exists and code needs to be written using it as a blueprint.

Action:
Use the FDD as the only source of truth. Each line in the FDD is either implemented, not started, or pending clarification.

Cursor Guidelines:

  • Mirror the structure of the FDD: implement in order unless directed otherwise.
  • Annotate the FDD inline as tasks are completed (e.g. ✅, ⏳, ❌).
  • Keep code minimal — FDD is the design, not a springboard for reinvention.
  • Reflect all edge cases and data shapes described in the FDD.

Tone: Tactical executor. Think “robot with a knife,” not “author with a pen.”

✍️ Cursor Rule #3: draft → FDD​

Rule Name: formalize-fdd-from-idea

Trigger: When Max drops a freeform idea, concept, or feature description meant to be shaped into an FDD.

Action:
Convert unstructured input into a minimal, structured FDD, preserving all specific details and nuances.

Cursor Guidelines:

  • Do not optimize, summarize, or generalize the idea.
  • Capture:
    • Intentions
    • User flows
    • Data inputs/outputs
    • Edge considerations
  • Add TODOs only if strictly necessary.
  • If uncertain about a point — include it as a comment, don’t discard it.

Tone: Legal scribe. Keep the original soul of the idea, just wrap it in clarity.

🧠 Cursor Rule #4: chat → FDD​

Rule Name: fdd-microadjust-from-chat

Trigger: When Max finishes a deep, detailed conversation with Cursor about a feature and wants the updated knowledge to be reflected in the corresponding FDD.

Action:
Apply minimal, surgical edits to the relevant FDD to reflect newly confirmed behaviors, insights, constraints, or decisions from the chat. Think: “What would future-me need to know to continue this?”

Cursor Guidelines:

  • Do not rewrite the FDD — update only what changed.
  • If context from the chat clarifies vague parts of the FDD — clarify them inline.
  • If the chat exposes an implicit assumption — make it explicit.
  • Use comments only if something is still under question.
  • Never add generic summaries or fluff.

Tone: Precision editor. Each word you change should reduce friction for Future Max.