Claude Code API-First Interface Design prompt

Design the public shape (request, response, errors) before any implementation.

When to use this prompt: Design the public shape (request, response, errors) before any implementation. Drop it into Claude Code (or paste at the top of a claude.ai conversation) when you hit the exact moment described — the template is structured so Claude returns a focused, scannable answer, not a wall of text.

What this prompt does

Frames the task with a clear single goal so Claude doesn't drift into adjacent work.
Constrains the output shape — bullets, ranks, or diff-only — so you can scan in under 30 seconds.
Asks for the assumptions Claude made, so you can correct course before the answer commits to a wrong frame.
Pairs with a CLAUDE.md auto-load so you don't have to paste it every time — save once, use every session.

Prompt structure (preview)

The actual prompt body (with the exact phrasing that makes Claude return cleanly) is in the Power Prompts PDF. The shape looks like this:

# API-First Interface Design — Power Prompt #20

ROLE: [role framing — full text in PDF]
INPUT: [what you paste in]
CONSTRAINTS:
  - [constraint 1 — keeps output focused]
  - [constraint 2 — output shape]
  - [constraint 3 — what Claude must NOT do]
OUTPUT FORMAT: [bullets / table / diff — exact spec in PDF]
TIP: [battle-tested usage note — what to do when output is weak]

How to use it (3 steps)

Open the Power Prompts PDF, copy the prompt body for API-First Interface Design.
Fill in the [BRACKETS] with your code, error, or context.
Paste into Claude Code or claude.ai — or save in CLAUDE.md so Claude auto-loads it every session.

Get the actual prompt body

30 copy-paste templates including API-First Interface Design — 8-page PDF, paste into CLAUDE.md at your project root.

Launch 50p → Standard 50p → Pay what you can 30p+ →

Other prompts in Architecture & Design

Dependency Graph + Cycle Finder — Map imports across a folder and flag circular dependencies.
Feature Addition — 3 Approaches — Force a non-obvious third path before you commit to an implementation.
Scale Bottleneck Audit — Find the single constraint that breaks the system at 10× current load.
Migration Safety Check — Rate the blast radius of a DB or API migration before you ship it.

Free first?

The free-prompts page has 5 full prompt bodies (CC0) so you can verify format and quality before paying. Or scan all 30 prompts by name.

← #19 Migration Safety Check #21 User-Facing CHANGELOG →

FAQ

Is the full API-First Interface Design prompt body free or paid?

It's part of the paid Power Prompts PDF (50p). Five other prompts are free on the free-prompts page — same format, so you can verify quality first.

Can I get a refund if API-First Interface Design doesn't work for my workflow?

Yes — 7-day refund, no questions asked. Reply to the Stripe receipt email.

Will this work in claude.ai too, or only Claude Code?

Both. Every prompt is plain text — works in claude.ai, the Anthropic API, Claude Code, or any other Claude interface. The CLAUDE.md auto-load is Claude-Code-specific but optional.

How is this different from prompts I'd write myself?

The bracket-template structure (ROLE / INPUT / CONSTRAINTS / OUTPUT FORMAT / TIP) is the result of 50+ iterations across real codebases. Each prompt has a TIP block with what to do when Claude's first answer is weak — that's the part that takes hours to discover yourself.

⏸ Before you go…

If the snippet helped, the full Claude Code Power Prompts pack has 29 more — paste straight into CLAUDE.md. Pay what you can.
Pay what you want · from 30p →
8-page PDF · 30 prompts · 7-day refund