--- title: "OpenAPI app builder" type: "skill" url: "https://useaiblocks.com/skills/build-an-app-from-an-openapi-spec" updated: "2026-10-28" first_published: "2026-10-25" job: "Build and ship software" tested: true licence: "MIT" source: "https://github.com/github/awesome-copilot/tree/613efc8c21d9b3ce642dff361d17006cd9967e28/skills/openapi-to-application-code" instructions: "https://useaiblocks.com/skills/build-an-app-from-an-openapi-spec/SKILL.md" --- # OpenAPI app builder > Share an OpenAPI spec and target stack. Get app code, tests and setup notes. Share your API spec and chosen stack. Check the contract, build the app and get code with tests and setup notes. Free skill for the job "Build and ship software" · Level: intermediate · Thinking: medium · Tested · Updated 2026-10-28 ## Links - Page: https://useaiblocks.com/skills/build-an-app-from-an-openapi-spec - Instructions (SKILL.md): https://useaiblocks.com/skills/build-an-app-from-an-openapi-spec/SKILL.md - All files (zip): https://useaiblocks.com/skills/build-an-app-from-an-openapi-spec.zip - JSON version: https://useaiblocks.com/skills/build-an-app-from-an-openapi-spec.json - In your AI: connect https://useaiblocks.com/mcp and ask "Use AI Blocks to get build-an-app-from-an-openapi-spec" ## What it does Share your API spec and chosen stack. Check the contract, build the app and get code with tests and setup notes. ## What you give it - Your OpenAPI spec as a link, a file or pasted text. - Your target framework and version, such as Node with Express. - Your login method, if the spec does not name one (optional). - Business rules the spec leaves open (optional). - Whether you want a database, Docker or pagination (optional). ## What you get - A project folder layout for your chosen framework. - Route handlers for every path and method in your spec. - Data types built from your spec's schemas. - Service code, tests and example requests. - A README, .gitignore and .env.example. - A list of gaps and unclear parts in your spec. ## Example: what goes in and what comes out ### What goes in - Your OpenAPI spec as a link, a file or pasted text - Your target framework and version - Your login method, such as API keys or JWT (optional) - Business rules the spec leaves open (optional) - Database and Docker choices (optional) ### Before you start - An AI that can write many files, or room in a chat to paste each file - A way to run code on your computer if you want to run the tests ### What comes out - **README.md**: How to set up, configure and run the app, and how to test the endpoints. - **Build config**: The framework's package or build file, such as package.json, pom.xml or build.gradle. - **Controllers**: Route handlers for each path and method in your spec, with validation and error handling. - **Services**: Business logic behind each route, kept apart from the HTTP layer. - **Models**: Data types built from the schemas in your spec. - **Repositories and config**: Data access code if you want a database, plus app settings and startup code. - **Tests**: Unit tests for controllers and services, plus example requests. - **.gitignore and .env.example**: Files that keep secrets out of git and list the settings the app needs. ## Use it when - You have an OpenAPI file and need a working server to start from. - A team has agreed the API design and now needs the first version of the code. - You want a fast mock server so front-end work can start. - You want to test whether your spec is complete by seeing what gets built. ## Skip it when - You have no spec and your API is hand-written: write the spec first in a spec design tool, or ask a developer to build it by hand. - Your spec is private and you cannot share it with an AI tool: ask a developer on your team to run a code generator locally. - You only need a client to call an API, not a server: use the client generator that comes with your framework. ## How to use it 1. Open Claude, ChatGPT or Gemini and paste the skill text, or add the skill folder if your tool takes files. 2. Paste your OpenAPI spec, or give a link if your AI can open web pages. 3. Say which framework and version you want. If you skip this, your AI should ask before it writes code. 4. Answer its questions about database, login method, Docker and tests. 5. Read the list of gaps in your spec, then check the routes against your spec. 6. Copy the files into a folder. To install and run the tests, you need code running on your own computer. ## What to do next - [Software developer from specifications](https://useaiblocks.com/skills/spec-builder): Build it - [API spec writer](https://useaiblocks.com/skills/api-spec-writer): Build it - [REST API designer](https://useaiblocks.com/skills/rest-api-designer): Build it ## Sources and credits - From github: https://github.com/github/awesome-copilot/tree/613efc8c21d9b3ce642dff361d17006cd9967e28/skills/openapi-to-application-code, shared under the MIT licence (original name: openapi-to-application-code). - [openapi-to-application-code skill](https://github.com/github/awesome-copilot/tree/613efc8c21d9b3ce642dff361d17006cd9967e28/skills/openapi-to-application-code), github: Original instructions and supporting files, with attribution and the MIT licence. Display copy describes the task. ## Instructions (SKILL.md) ## Generate Application from OpenAPI Spec Your goal is to generate a complete, working application from an OpenAPI specification using the active framework's conventions and best practices. ### Before you start Use the material below to do this job. If facts or tool access are missing, explain what you can finish and what must wait. **What you need** (use your own material or the linked skill): - **Your API spec** (yours): the API's endpoints, data shapes, sign-in method and errors, such as an OpenAPI file. **Makes it better (optional):** - **Your question** (yours): the decision or problem, and what a good outcome looks like. How to start: 1. **Look first.** Use what they've already attached, pasted or put in their about-me note. In a coding assistant with file access, look in the project too for these by name. 2. **Check what's missing.** Look for your API spec, your question. They can attach files, paste the details, or share a file path your assistant can read. Ask only for missing facts that change the result. If they ask you to start with what they have, complete the parts you can and mark the gaps. 3. **Do the job.** Follow the skill below with the facts and tools you have. Mark each gap with `MISSING:` where it belongs and never invent a fact to fill it. ### Input Requirements 1. **OpenAPI Specification**: Provide either: - A URL to the OpenAPI spec (e.g., `https://api.example.com/openapi.json`) - A local file path to the OpenAPI spec - The full OpenAPI specification content pasted directly 2. **Project Details** (if not in spec): - Project name and description - Target framework and version - Package/namespace naming conventions - Authentication method (if not specified in OpenAPI) ### Generation Process #### Step 1: Analyze the OpenAPI Specification - Validate the OpenAPI spec for completeness and correctness - Identify all endpoints, HTTP methods, request/response schemas - Extract authentication requirements and security schemes - Note data model relationships and constraints - Flag any ambiguities or incomplete definitions #### Step 2: Design Application Architecture - Plan directory structure appropriate for the framework - Identify controller/handler grouping by resource or domain - Design service layer organization for business logic - Plan data models and entity relationships - Design configuration and initialization strategy #### Step 3: Generate Application Code - Create project structure with build/package configuration files - Generate models/DTOs from OpenAPI schemas - Generate controllers/handlers with route mappings - Generate service layer with business logic - Generate repository/data access layer if applicable - Add error handling, validation, and logging - Generate configuration and startup code #### Step 4: Add Supporting Files - Generate appropriate unit tests for services and controllers - Create README with setup and running instructions - Add .gitignore and environment configuration templates - Generate API documentation files - Create example requests/integration tests ### Output Structure The generated application will include: ``` project-name/ ├── README.md # Setup and usage instructions ├── [build-config] # Framework-specific build files (pom.xml, build.gradle, package.json, etc.) ├── src/ │ ├── main/ │ │ ├── [language]/ │ │ │ ├── controllers/ # HTTP endpoint handlers │ │ │ ├── services/ # Business logic │ │ │ ├── models/ # Data models and DTOs │ │ │ ├── repositories/ # Data access (if applicable) │ │ │ └── config/ # Application configuration │ │ └── resources/ # Configuration files │ └── test/ │ ├── [language]/ │ │ ├── controllers/ # Controller tests │ │ └── services/ # Service tests │ └── resources/ # Test configuration ├── .gitignore ├── .env.example # Environment variables template └── docker-compose.yml # Optional: Docker setup (if applicable) ``` ### Best Practices Applied - **Framework Conventions**: Follows framework-specific naming, structure, and patterns - **Separation of Concerns**: Clear layers with controllers, services, and repositories - **Error Handling**: Comprehensive error handling with meaningful responses - **Validation**: Input validation and schema validation throughout - **Logging**: Structured logging for debugging and monitoring - **Testing**: Unit tests for services and controllers - **Documentation**: Inline code documentation and setup instructions - **Security**: Implements authentication/authorization from OpenAPI spec - **Scalability**: Design patterns support growth and maintenance ### Next Steps After generation: 1. Review the generated code structure and make customizations as needed 2. Install dependencies according to framework requirements 3. Configure environment variables and database connections 4. Run tests to verify generated code 5. Start the development server 6. Test endpoints using the provided examples ### After this When you've handed it back, suggest what they could do next in one short question. It's a suggestion: if they're done, that's fine. Offer these, and say they can type their own: - The [Software developer from specifications](https://useaiblocks.com/skills/spec-builder). It takes the document and codebase. - The [API spec writer](https://useaiblocks.com/skills/api-spec-writer). It takes the codebase. - The [REST API designer](https://useaiblocks.com/skills/rest-api-designer). It takes the codebase. If they pick one and that skill is added here, carry straight on with what you just made. If not, give the link and say what to bring. ### Questions to Ask if Needed - Should the application include database/ORM setup, or just in-memory/mock data? - Do you want Docker configuration for containerization? - Should authentication be JWT, OAuth2, API keys, or basic auth? - Do you need integration tests or just unit tests? - Any specific database technology preferences? - Should the API include pagination, filtering, and sorting examples?