The build-decision guide for the AI era
Should it be a
prompt?
Or a skill, an MCP server, an agent, a real app, or nothing at all. Answer eight questions and get a verdict with the reasoning, the trade-offs and a first step.
By Mahmoud Halat, founder of Space & Story. Free, no sign-up, no model call: the logic is published.
- 6App / systemWeeks to months
- 5AgentDays to weeks
- 4MCP / connectorHours to days
- 3SkillAn afternoon
- 2Saved promptUnder an hour
- 1PromptMinutes
Step one
Run your task up the ladder
Eight questions. The cheapest rung that works wins, and every verdict shows the rule that set it. How the rules work.
What the patterns say
15 of 38 everyday tasks are skills. Only 7 need an agent or an app.
We ran 38 common work tasks, from meeting notes to invoice matching, through the same rules as the tool. Most land low on the ladder: packaged instructions beat software far more often than the hype suggests. Each one has its reasoning and a starting point.
Open the pattern library- PromptAlt text for a site's image backlog · Explaining one clause you don't understand
- Saved promptWeekly status update to your manager · Social posts from a new blog article
- SkillMeeting transcript to summary and action items · Proposal and quote drafting
- MCP / connectorWeekly KPI report from your analytics · Sales call prep brief
- AgentInbound lead triage and routing · Churn-risk alerts for account managers
- App / systemThree-way invoice matching (PO, receipt, invoice) · Personalised cold outreach at scale
- Don't buildCategorising expenses and bank transactions · Drafting replies in your own inbox
The explainer
Prompt vs skill vs MCP server vs agent vs app: what each one is, what it costs, when it breaks.
Read the definitions| Rung | First version | Upkeep |
|---|---|---|
| Prompt | Minutes | None |
| Saved prompt | Under an hour | Edit when your process changes |
| Skill | An afternoon | An owner, a version, a test case or two |
| MCP / connector | Hours to days | Auth, permissions, API changes |
| Agent | Days to weeks | Evals, logs, cost limits, someone on call |
| App / system | Weeks to months | A team or a vendor, forever |
Comparisons
Comparisons, from published specs
Prices and features checked against official pages in October 2026, with links.
- 01Claude Skills vs custom GPTs vs Gemini Gems vs Copilot agentsWhat Claude Skills, custom GPTs, Gemini Gems (now Gemini skills) and Microsoft 365 Copilot agents can do, who can build and share them, and the plan you need. Checked Oct 2026.
- 02AI app builders compared: Lovable, Bolt, v0, Replit Agent, Claude Code and CursorSix AI app builders compared on pricing (checked Oct 2026), strengths, weak spots and who should pick which, plus the signs you've outgrown them.
- 03Where to find Claude skills and MCP serversAnthropic's skills repo, Claude's directory, skills.sh, Skillspace, the official MCP Registry, Glama, Smithery and mcp.so compared on size, quality signals and safety.
Essays
The Moat Line essays
The other half of the question: once you can build it in a weekend, can anyone else?