Sample: typespec-first-development - TypeSpec-first API workflow with LLM

[Copilot]

• Create sample directory typespec-first-development under samples/
• Create Dev Proxy configuration file with TypeSpecGeneratorPlugin
• Create configuration file with local LLM support for enhanced descriptions
• Create README.md following template structure
• Create assets/sample.json metadata file
• Create placeholder note for screenshot in assets folder
• Update sample to comply with .github/copilot-instructions.md
• Update author to waldekmastykarz
• Update dates (creationDateTime and updateDateTime) to 2026-01-10
• Move config files to .devproxy folder
• Remove properties with default values (rate: 0)
• Use JSONPlaceholder API in README examples for quick testing

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Sample: typespec-first-development - TypeSpec-first API workflow with LLM</issue_title>
<issue_description>## Summary
Create a sample demonstrating TypeSpec-first API development workflow with Dev Proxy.

Plugins to use

• TypeSpecGeneratorPlugin - generates TypeSpec from traffic
• Local language model configuration for better descriptions

What to build

• Generate TypeSpec from existing API traffic
• Show improved results when using local LLM
• Complete workflow:
  1. Record API traffic → TypeSpec
  2. TypeSpec → OpenAPI
  3. OpenAPI → Client SDKs
• Compare TypeSpec output with and without LLM

Without LLM

op operation1(): string;

With LLM

@doc("Retrieves a list of all customers")
op getCustomers(): Customer[];

Why this is compelling

Modern API-first workflow. Better starting point for API design with AI-enhanced descriptions.

Reference docs

• TypeSpecGeneratorPlugin technical reference
• Generate TypeSpec file how-to guide
• Use a local language model how-to guide
  </issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Sample: typespec-first-development - TypeSpec-first API workflow with LLM #35

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[waldekmastykarz]

@copilot please review and update this sample to comply with the updated .github/copilot-instructions.md

[Copilot]

@copilot please review and update this sample to comply with the updated .github/copilot-instructions.md

Updated the sample in commit 326aba5. Changes made:

• Removed the "Test with a sample API" section from README.md (per "No test scripts" guideline)
• Added version history entry
• Updated updateDateTime in sample.json metadata

[github-actions]

Validation failed!

File: samples/typespec-first-development/assets/sample.json

• Invalid value 'https://github.com/copilot.png' for author's 'pictureUrl' property: The provided URL is not responding correctly!
• Invalid url for thumbnail Fixes npm start issue on Windows #1 property: The provided URL is not responding correctly!

[waldekmastykarz]

@copilot please also:

• Change the author in assets/sample.json to waldekmastykarz
• Update the sample dates (creationDateTime and updateDateTime) to 2026-01-10

[Copilot]

@copilot please also:

• Change the author in assets/sample.json to waldekmastykarz
• Update the sample dates (creationDateTime and updateDateTime) to 2026-01-10

Done in 50bed56. Updated author to waldekmastykarz and both dates to 2026-01-10 in assets/sample.json, and also updated the Contributors section in README.md to match.

[waldekmastykarz]

@copilot One more thing: please update the screenshot in assets/screenshot.png to reflect the current sample output.

[Copilot]

@copilot One more thing: please update the screenshot in assets/screenshot.png to reflect the current sample output.

I'm unable to create a screenshot as I don't have Dev Proxy installed in this environment to run the sample and capture the output. The screenshot would need to be created manually by:

1. Running devproxy --config-file generate-typespec.json --urls-to-watch "https://jsonplaceholder.typicode.com/*" --record
2. Making API requests through the proxy
3. Stopping Dev Proxy to generate the TypeSpec file
4. Capturing a screenshot showing the terminal output and generated TypeSpec file

Would you be able to provide the screenshot, or should I update the README to remove the screenshot reference until one is available?

[waldekmastykarz]

@copilot Please make the following changes:

1. Move all Dev Proxy config files to the .devproxy folder - All configuration files (like devproxyrc.json, mock files, error files, etc.) should be placed in a .devproxy subfolder within the sample directory. This is the recommended location for Dev Proxy configs.

2. Remove properties with default values - Keep the configuration files lean by removing any properties that are set to their default values. For example:

   • Remove "rate": 50 for error plugins if using the default rate
   • Remove any other properties where the value matches the Dev Proxy default
   • Note: Keep "enabled": true on plugins - we preserve this for easy toggling

This keeps the sample configs minimal and easier to understand.

[Copilot]

@copilot Please make the following changes:

1. Move all Dev Proxy config files to the .devproxy folder - All configuration files (like devproxyrc.json, mock files, error files, etc.) should b...

Done in 870a651:

• Moved both config files to .devproxy/ folder
• Removed "rate": 0 from both config files (kept "enabled": true on plugins)
• Updated README.md with the new config file paths

[waldekmastykarz]

@copilot

[waldekmastykarz]

@copilot use JSONPlaceholder API so that folks can quickly see this in action without having to standup an API or modify anything.

[Copilot]

Updated in 6b89b18. Changed to use JSONPlaceholder API (https://jsonplaceholder.typicode.com/*) and added sample curl commands with the correct proxy syntax (curl -ikx http://127.0.0.1:8000).

[waldekmastykarz]

@copilot use JSONPlaceholder

[Copilot]

Updated in 6b89b18.

[waldekmastykarz]

@copilot Please use the validation skill to validate this Dev Proxy sample. Check the sample structure, config files, metadata, and README for any issues. If you find problems, please fix them.

[Copilot]

@copilot Please use the validation skill to validate this Dev Proxy sample. Check the sample structure, config files, metadata, and README for any issues. If you find problems, please fix them.

Validated the sample against repository guidelines. All checks pass:

✅ Sample Structure

• .devproxy/ folder with config files
• README.md, assets/sample.json present

✅ Configuration Files

• Correct $schema (v2.0.0)
• TypeSpecGeneratorPlugin configured correctly
• LLM config has proper languageModel section
• No default values included

✅ README.md

• Compatibility badge, version history, tracking pixel
• Correct curl syntax (-ikx http://127.0.0.1:8000)
• JSONPlaceholder API for quick testing

✅ Metadata (assets/sample.json)

• All required fields present
• pnp-devproxy-* naming pattern
• shortDescription/longDescription match
• Dates in YYYY-MM-DD format
• Complete metadata section

⚠️ Known Issue

• screenshot.png missing - requires manual creation (previously discussed)

[waldekmastykarz]

Closing - single plugin config, docs already cover this with the TypeSpec how-to guide.