spec-driven-development

Name: spec-driven-development
Author: addyosmani

byaddyosmani· 31 skills

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How to install spec-driven-development?

addyosmani/agent-skills/spec-driven-development

$npx -y skills add addyosmani/agent-skills --skill spec-driven-development

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Run `npx skills use "https://github.com/addyosmani/agent-skills" --skill "addyosmani/agent-skills/spec-driven-development"` and follow the generated skill instructions now. Read its complete output, redirecting it to a temporary file first if necessary. Resolve relative paths from the supporting-files directory it provides.

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Use the skills in "https://github.com/addyosmani/agent-skills" that are relevant to the current task. Run `npx skills add "https://github.com/addyosmani/agent-skills"` and select the relevant skills, then follow their instructions.

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SKILL.md

1	# Spec-Driven Development
2
3	## Overview
4
5	Write a structured specification before writing any code. The spec is the shared source of truth between you and the human engineer — it defines what we're building, why, and how we'll know it's done. Code without a spec is guessing.
6
7	## When to Use
8
9	- Starting a new project or feature
10	- Requirements are ambiguous or incomplete
11	- The change touches multiple files or modules
12	- You're about to make an architectural decision
13	- The task would take more than 30 minutes to implement
14
15	When NOT to use: Single-line fixes, typo corrections, or changes where requirements are unambiguous and self-contained.
16
17	## The Gated Workflow
18
19	Spec-driven development has four phases. Do not advance to the next phase until the current one is validated.
20
21	```
22	SPECIFY ──→ PLAN ──→ TASKS ──→ IMPLEMENT
23	│ │ │ │
24	▼ ▼ ▼ ▼
25	Human Human Human Human
26	reviews reviews reviews reviews
27	```
28
29	### Phase 1: Specify
30
31	Start with a high-level vision. Ask the human clarifying questions until requirements are concrete.
32
33	Surface assumptions immediately. Before writing any spec content, list what you're assuming:
34
35	```
36	ASSUMPTIONS I'M MAKING:
37	1. This is a web application (not native mobile)
38	2. Authentication uses session-based cookies (not JWT)
39	3. The database is PostgreSQL (based on existing Prisma schema)
40	4. We're targeting modern browsers only (no IE11)
41	→ Correct me now or I'll proceed with these.
42	```
43
44	Don't silently fill in ambiguous requirements. The spec's entire purpose is to surface misunderstandings before code gets written — assumptions are the most dangerous form of misunderstanding.
45
46	Write a spec document covering these six core areas:
47
48	1. Objective — What are we building and why? Who is the user? What does success look like?
49
50	2. Commands — Full executable commands with flags, not just tool names.
51	```
52	Build: npm run build
53	Test: npm test -- --coverage
54	Lint: npm run lint --fix
55	Dev: npm run dev
56	```
57
58	3. Project Structure — Where source code lives, where tests go, where docs belong.
59	```
60	src/ → Application source code
61	src/components → React components
62	src/lib → Shared utilities
63	tests/ → Unit and integration tests
64	e2e/ → End-to-end tests
65	docs/ → Documentation
66	```
67
68	4. Code Style — One real code snippet showing your style beats three paragraphs describing it. Include naming conventions, formatting rules, and examples of good output.
69
70	5. Testing Strategy — What framework, where tests live, coverage expectations, which test levels for which concerns.
71
72	6. Boundaries — Three-tier system:
73	- Always do: Run tests before commits, follow naming conventions, validate inputs
74	- Ask first: Database schema changes, adding dependencies, changing CI config
75	- Never do: Commit secrets, edit vendor directories, remove failing tests without approval
76
77	Spec template:
78
79	```markdown
80	# Spec: [Project/Feature Name]
81
82	## Objective
83	[What we're building and why. User stories or acceptance criteria.]
84
85	## Tech Stack
86	[Framework, language, key dependencies with versions]
87
88	## Commands
89	[Build, test, lint, dev — full commands]
90
91	## Project Structure
92	[Directory layout with descriptions]
93
94	## Code Style
95	[Example snippet + key conventions]
96
97	## Testing Strategy
98	[Framework, test locations, coverage requirements, test levels]
99
100	## Boundaries
101	- Always: [...]
102	- Ask first: [...]
103	- Never: [...]
104
105	## Success Criteria
106	[How we'll know this is done — specific, testable conditions]
107
108	## Open Questions
109	[Anything unresolved that needs human input]
110	```
111
112	Reframe instructions as success criteria. When receiving vague requirements, translate them into concrete conditions:
113
114	```
115	REQUIREMENT: "Make the dashboard faster"
116
117	REFRAMED SUCCESS CRITERIA:
118	- Dashboard LCP < 2.5s on 4G connection
119	- Initial data load completes in < 500ms
120	- No layout shift during load (CLS < 0.1)
121	→ Are these the right targets?
122	```
123
124	This lets you loop, retry, and problem-solve toward a clear goal rather than guessing what "faster" means.
125
126	### Phase 2: Plan
127
128	With the validated spec, generate a technical implementation plan:
129
130	1. Identify the major components and their dependencies
131	2. Determine the implementation order (what must be built first)
132	3. Note risks and mitigation strategies
133	4. Identify what can be built in parallel vs. what must be sequential
134	5. Define verification checkpoints between phases
135
136	> Follow `planning-and-task-breakdown` for the dependency-graph mapping and vertical-slicing mechanics behind these steps; it is the canonical source. The bullets above are a lightweight summary; if they ever diverge, `planning-and-task-breakdown` takes precedence.
137	>
138	> Output convention: Save the plan to `tasks/plan.md` and the task list to `tasks/todo.md`, per the `/plan` command convention. Create `tasks/` if it does not exist. Downstream commands (`/build`, etc.) expect these paths.
139
140	The plan should be reviewable: the human should be able to read it and say "yes, that's the right approach" or "no, change X."
141
142	### Phase 3: Tasks
143
144	Break the plan into discrete, implementable tasks:
145
146	- Each task should be completable in a single focused session
147	- Each task has explicit acceptance criteria
148	- Each task includes a verification step (test, build, manual check)
149	- Tasks are ordered by dependency, not by perceived importance
150	- No task should require changing more than ~5 files
151
152	> Follow `planning-and-task-breakdown` for the full task-sizing and dependency-ordering mechanics; it is the canonical source. The template below is a lightweight inline form; if they ever diverge, `planning-and-task-breakdown` takes precedence.
153
154	Task template:
155	```markdown
156	- [ ] Task: [Description]
157	- Acceptance: [What must be true when done]
158	- Verify: [How to confirm — test command, build, manual check]
159	- Files: [Which files will be touched]
160	```
161
162	### Phase 4: Implement
163
164	Execute tasks one at a time following `skills/incremental-implementation/SKILL.md` (`incremental-implementation`) and `skills/test-driven-development/SKILL.md` (`test-driven-development`). Use `skills/context-engineering/SKILL.md` (`context-engineering`) to load the right spec sections and source files at each step rather than flooding the agent with the entire spec.
165
166	## Keeping the Spec Alive
167
168	The spec is a living document, not a one-time artifact:
169
170	- Update when decisions change — If you discover the data model needs to change, update the spec first, then implement.
171	- Update when scope changes — Features added or cut should be reflected in the spec.
172	- Commit the spec — The spec belongs in version control alongside the code.
173	- Reference the spec in PRs — Link back to the spec section that each PR implements.
174
175	## Common Rationalizations
176
177	\| Rationalization \| Reality \|
178	\|---\|---\|
179	\| "This is simple, I don't need a spec" \| Simple tasks don't need long specs, but they still need acceptance criteria. A two-line spec is fine. \|
180	\| "I'll write the spec after I code it" \| That's documentation, not specification. The spec's value is in forcing clarity before code. \|
181	\| "The spec will slow us down" \| A 15-minute spec prevents hours of rework. Waterfall in 15 minutes beats debugging in 15 hours. \|
182	\| "Requirements will change anyway" \| That's why the spec is a living document. An outdated spec is still better than no spec. \|
183	\| "The user knows what they want" \| Even clear requests have implicit assumptions. The spec surfaces those assumptions. \|
184
185	## Red Flags
186
187	- Starting to write code without any written requirements
188	- Asking "should I just start building?" before clarifying what "done" means
189	- Implementing features not mentioned in any spec or task list
190	- Making architectural decisions without documenting them
191	- Skipping the spec because "it's obvious what to build"
192
193	## Verification
194
195	Before proceeding to implementation, confirm:
196
197	- [ ] The spec covers all six core areas
198	- [ ] The human has reviewed and approved the spec
199	- [ ] Success criteria are specific and testable
200	- [ ] Boundaries (Always/Ask First/Never) are defined
201	- [ ] The spec is saved to a file in the repository

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Type

Run `npx skills use "https://github.com/addyosmani/agent-skills" --skill "addyosmani/agent-skills/spec-driven-development"` and follow the generated skill instructions now. Read its complete output, redirecting it to a temporary file first if necessary. Resolve relative paths from the supporting-files directory it provides.

Use the skills in "https://github.com/addyosmani/agent-skills" that are relevant to the current task. Run `npx skills add "https://github.com/addyosmani/agent-skills"` and select the relevant skills, then follow their instructions.

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