TypeSpec Create API Plugin

An AI skill that generates TypeSpec API plugin definitions, creating typed plugin configurations that extend API functionality with middleware, authentication, rate limiting, and custom processing logic through the TypeSpec contract language.

What Is This?

Overview

This skill produces TypeSpec definitions for API plugins that hook into request and response pipelines. It generates typed plugin interfaces, configuration schemas, middleware chain definitions, and extension point contracts. The output specifies how plugins interact with the host API, what configuration they accept, and what guarantees they provide, all expressed in TypeSpec so that plugin contracts compile into verifiable schemas and documentation.

Who Should Use This

Designed for API platform developers building extensible service architectures, teams creating plugin ecosystems for their APIs, and developers who want typed contracts governing how third party extensions integrate with their services.

Why Use It?

Problems It Solves

API plugins often break because their interfaces are defined informally through documentation or convention. When the host API changes, plugins fail silently or produce unexpected behavior. Without typed contracts, plugin developers guess at parameter types, configuration formats, and lifecycle hooks. TypeSpec definitions formalize these interfaces so mismatches are caught at compile time.

Core Highlights

• Plugin Interface Contracts defines typed extension points for API middleware
• Configuration Schemas generates validated configuration types for each plugin
• Lifecycle Hooks specifies typed interfaces for request and response processing
• Versioned Contracts supports API plugin versioning with compatibility checks
• SDK Generation compiles plugin specs into development kits for plugin authors

How to Use It?

Basic Usage

Describe the plugin capabilities and receive complete TypeSpec definitions.

// Generated: plugins/rate-limiter.tsp
import "@typespec/http";

model RateLimitConfig {
  maxRequests: int32;
  windowSeconds: int32;
  keyStrategy: "ip" | "apiKey" | "userId";
  burstAllowance?: int32;
}

model RateLimitResult {
  allowed: boolean;
  remaining: int32;
  resetAt: utcDateTime;
}

@route("/plugins/rate-limiter")
namespace RateLimiterPlugin {
  @post op check(@body request: RateLimitCheck): RateLimitResult;
  @get op config(): RateLimitConfig;
  @put op updateConfig(@body config: RateLimitConfig): RateLimitConfig;
}

Real-World Examples

API Gateway Plugin System

A platform team built an extensible API gateway and used this skill to define contracts for authentication, caching, transformation, and logging plugins. Each plugin had a typed contract specifying its configuration, the request lifecycle hooks it could participate in, and the response modifications it was allowed to make.

// Generated: plugins/auth-plugin.tsp
model AuthPluginConfig {
  provider: "jwt" | "oauth2" | "apiKey";
  tokenHeader: string;
  requiredScopes?: string[];
}

model AuthContext {
  userId: string;
  scopes: string[];
  expiresAt: utcDateTime;
}

interface ApiPlugin {
  @doc("Called before request reaches handler")
  op onRequest(@body ctx: RequestContext): AuthContext | ErrorResponse;

  @doc("Plugin configuration schema")
  op getConfig(): AuthPluginConfig;
}

Advanced Tips

Create a base plugin interface that all plugins must implement, then extend it with specialized contracts for each plugin type. Use TypeSpec decorators to annotate required permissions and performance constraints. Version plugin contracts independently from the host API.

When to Use It?

Use Cases

• API Gateway Extensions define typed middleware for request processing pipelines
• Plugin Marketplaces create formal contracts for third party API extensions
• Authentication Plugins specify typed auth provider interfaces
• Transformation Plugins define request and response modification contracts
• Monitoring Plugins create typed interfaces for metrics and logging extensions

Related Topics

When creating API plugin definitions, these prompts activate the skill:

• "Create a TypeSpec API plugin definition"
• "Define a plugin interface in TypeSpec"
• "Generate typed middleware contracts"
• "Build a TypeSpec spec for API extensions"

Important Notes

Requirements

• TypeSpec compiler for generating output schemas from plugin definitions
• Understanding of API middleware and plugin architecture patterns
• Target output format selected for plugin SDK generation
• Works with any API framework that supports middleware extension

Usage Recommendations

Do:

• Define strict input and output types for all plugin lifecycle hooks
• Version plugin contracts so updates do not break existing plugins
• Generate SDKs from compiled specs for plugin developer convenience
• Test plugins against the typed contract before deployment

Don't:

• Use untyped parameters in plugin interfaces as this defeats type safety
• Change plugin contracts without versioning and migration guidance
• Skip error type definitions as plugins must handle failures gracefully
• Couple plugin contracts to implementation since they should remain abstract

Limitations

• TypeSpec plugin patterns are still emerging in the community
• Complex plugin lifecycles with async callbacks may need manual TypeSpec authoring
• Generated contracts define interfaces but not runtime plugin behavior
• Plugin performance characteristics cannot be expressed in type contracts alone