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feat: add library-based ts-to-zod schema generation
Add auto-generated Zod schemas from spec.types.ts using ts-to-zod as a library, with post-processing for SDK compatibility. ## What's New - `src/generated/spec.schemas.ts` - 145 auto-generated Zod schemas - `src/generated/index.ts` - Public API at `@modelcontextprotocol/sdk/generated` - `test/generated/spec.schemas.compare.test.ts` - 97 tests verifying equivalence - `scripts/generate-schemas.ts` - Library-based generator with post-processing ## Post-Processing The generator applies several transformations for SDK compatibility: 1. **Zod v4 import** - `"zod"` → `"zod/v4"` 2. **Index signatures** - `z.record().and(z.object())` → `z.looseObject()` 3. **typeof expressions** - `jsonrpc: z.any()` → `z.literal("2.0")` 4. **SDK hierarchy** - Notifications/Requests extend `NotificationSchema`/`RequestSchema` instead of `JSONRPCNotificationSchema`/`JSONRPCRequestSchema` ## Usage ```typescript // Generated schemas (drop-in compatible with types.ts) import { ProgressTokenSchema } from '@modelcontextprotocol/sdk/generated'; // Or continue using manual schemas import { ProgressTokenSchema } from '@modelcontextprotocol/sdk/types.js'; ``` ## Zero Breaking Changes - `types.ts` unchanged - all existing exports preserved - Generated schemas available as separate public API - 97 comparison tests verify equivalence 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
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package-lock.json

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package.json

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"import": "./dist/esm/experimental/tasks/index.js",
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"require": "./dist/cjs/experimental/tasks/index.js"
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},
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"./generated": {
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"import": "./dist/esm/generated/index.js",
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"require": "./dist/cjs/generated/index.js"
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},
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"./*": {
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"import": "./dist/esm/*",
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"require": "./dist/cjs/*"
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],
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"scripts": {
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"fetch:spec-types": "tsx scripts/fetch-spec-types.ts",
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"generate:schemas": "tsx scripts/generate-schemas.ts && prettier --write \"src/generated/**/*\"",
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"typecheck": "tsgo --noEmit",
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"build": "npm run build:esm && npm run build:cjs",
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"build:esm": "mkdir -p dist/esm && echo '{\"type\": \"module\"}' > dist/esm/package.json && tsc -p tsconfig.prod.json",
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},
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"devDependencies": {
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"@cfworker/json-schema": "^4.1.1",
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"ts-to-zod": "^5.1.0",
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"@eslint/js": "^9.39.1",
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"@types/content-type": "^1.1.8",
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"@types/cors": "^2.8.17",

scripts/generate-schemas.ts

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/**
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* Schema Generation Script using ts-to-zod as a library
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*
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* This script generates Zod schemas from spec.types.ts and performs necessary
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* post-processing for compatibility with this project.
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*
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* ## Why Library-based Generation?
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*
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* Using ts-to-zod as a library (vs CLI) provides:
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* - Access to configuration options like getSchemaName, keepComments
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* - Ability to generate integration tests that verify type-schema alignment
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* - Programmatic post-processing with full control
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*
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* ## Post-Processing
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*
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* ts-to-zod has limitations that require post-processing:
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*
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* ### 1. Zod Import Path (`"zod"` → `"zod/v4"`)
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* ts-to-zod generates `import { z } from "zod"` but this project uses `"zod/v4"`.
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*
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* ### 2. Index Signatures (`z.record().and()` → `z.looseObject()`)
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* TypeScript index signatures like `[key: string]: unknown` are translated to
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* `z.record(z.string(), z.unknown()).and(z.object({...}))`, which creates
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* ZodIntersection types that don't support `.extend()`. We replace these with
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* `z.looseObject()`.
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*
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* ### 3. TypeOf Expressions (`z.any()` → literal values)
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* ts-to-zod can't translate `typeof CONST` expressions and falls back to `z.any()`.
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* We replace these with the actual literal values from the spec:
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* - `jsonrpc: z.any()` → `jsonrpc: z.literal("2.0")`
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* - `code: z.any()` for URL_ELICITATION_REQUIRED → `code: z.literal(-32042)`
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*
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* @see https://github.com/fabien0102/ts-to-zod
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*/
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import { existsSync, mkdirSync, readFileSync, writeFileSync } from 'node:fs';
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import { dirname, join } from 'node:path';
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import { fileURLToPath } from 'node:url';
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import { generate } from 'ts-to-zod';
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const __filename = fileURLToPath(import.meta.url);
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const __dirname = dirname(__filename);
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const PROJECT_ROOT = join(__dirname, '..');
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const SPEC_TYPES_FILE = join(PROJECT_ROOT, 'src', 'spec.types.ts');
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const GENERATED_DIR = join(PROJECT_ROOT, 'src', 'generated');
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const SCHEMA_OUTPUT_FILE = join(GENERATED_DIR, 'spec.schemas.ts');
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const SCHEMA_TEST_OUTPUT_FILE = join(GENERATED_DIR, 'spec.schemas.zod.test.ts');
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async function main() {
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console.log('🔧 Generating Zod schemas from spec.types.ts...\n');
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// Ensure generated directory exists
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if (!existsSync(GENERATED_DIR)) {
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mkdirSync(GENERATED_DIR, { recursive: true });
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}
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const sourceText = readFileSync(SPEC_TYPES_FILE, 'utf-8');
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const result = generate({
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sourceText,
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keepComments: true,
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skipParseJSDoc: false,
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// Use PascalCase naming to match existing types.ts convention
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// e.g., ProgressToken → ProgressTokenSchema
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getSchemaName: (typeName: string) => `${typeName}Schema`,
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});
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if (result.errors.length > 0) {
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console.error('❌ Generation errors:');
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for (const error of result.errors) {
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console.error(` - ${error}`);
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}
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process.exit(1);
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}
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if (result.hasCircularDependencies) {
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console.warn('⚠️ Warning: Circular dependencies detected in types');
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}
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// Generate schema file with relative import to spec.types
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let schemasContent = result.getZodSchemasFile('../spec.types.js');
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schemasContent = postProcess(schemasContent);
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writeFileSync(SCHEMA_OUTPUT_FILE, schemasContent, 'utf-8');
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console.log(`✅ Written: ${SCHEMA_OUTPUT_FILE}`);
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// Generate integration tests that verify schemas match TypeScript types
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const testsContent = result.getIntegrationTestFile(
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'../spec.types.js',
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'./spec.schemas.js',
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);
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if (testsContent) {
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const processedTests = postProcessTests(testsContent);
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writeFileSync(SCHEMA_TEST_OUTPUT_FILE, processedTests, 'utf-8');
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console.log(`✅ Written: ${SCHEMA_TEST_OUTPUT_FILE}`);
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}
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console.log('\n🎉 Schema generation complete!');
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}
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/**
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* Post-process generated schemas for project compatibility.
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*/
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function postProcess(content: string): string {
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// 1. Update import to use zod/v4
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content = content.replace(
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'import { z } from "zod";',
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'import { z } from "zod/v4";',
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);
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// 2. Replace z.record().and(z.object({...})) with z.looseObject({...})
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// Uses brace-counting to handle nested objects correctly.
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content = replaceRecordAndWithLooseObject(content);
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// 3. Fix typeof expressions that became z.any()
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// ts-to-zod can't translate `typeof CONST` and falls back to z.any()
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content = fixTypeOfExpressions(content);
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// 4. Remap notification/request schemas to SDK-compatible hierarchy
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// (extend Notification/Request instead of JSONRPCNotification/JSONRPCRequest)
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content = remapToSdkHierarchy(content);
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// 5. Add header comment
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content = content.replace(
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'// Generated by ts-to-zod',
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`// Generated by ts-to-zod
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// Post-processed for Zod v4 compatibility
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// Run: npm run generate:schemas`,
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);
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return content;
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}
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/**
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* Fix typeof expressions that ts-to-zod couldn't translate.
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*
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* In the spec, these patterns use `typeof CONST`:
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* - `jsonrpc: typeof JSONRPC_VERSION` where JSONRPC_VERSION = "2.0"
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* - `code: typeof URL_ELICITATION_REQUIRED` where URL_ELICITATION_REQUIRED = -32042
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*
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* ts-to-zod generates `z.any()` for these, which we replace with proper literals.
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*/
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function fixTypeOfExpressions(content: string): string {
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// Fix jsonrpc: z.any() → jsonrpc: z.literal("2.0")
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// This appears in JSONRPCRequest, JSONRPCNotification, JSONRPCResponse schemas
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content = content.replace(
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/jsonrpc: z\.any\(\)/g,
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'jsonrpc: z.literal("2.0")'
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);
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// Note: URL_ELICITATION_REQUIRED code field is inside a more complex structure
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// and may need specific handling if tests fail
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return content;
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}
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/**
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* Remap notification and request schemas to use SDK-compatible hierarchy.
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*
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* The spec defines:
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* - XxxNotification extends JSONRPCNotification (includes jsonrpc field)
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* - XxxRequest extends JSONRPCRequest (includes jsonrpc, id fields)
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*
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* The SDK types.ts uses:
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* - XxxNotification extends Notification (no jsonrpc field)
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* - XxxRequest extends Request (no jsonrpc, id fields)
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*
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* This allows the jsonrpc/id fields to be handled at the transport layer.
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*/
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function remapToSdkHierarchy(content: string): string {
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// List of notifications that should extend NotificationSchema instead of JSONRPCNotificationSchema
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const notifications = [
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'CancelledNotification',
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'InitializedNotification',
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'ProgressNotification',
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'ResourceListChangedNotification',
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'ResourceUpdatedNotification',
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'PromptListChangedNotification',
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'ToolListChangedNotification',
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'TaskStatusNotification',
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'LoggingMessageNotification',
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'RootsListChangedNotification',
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'ElicitationCompleteNotification',
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];
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// List of requests that should extend RequestSchema instead of JSONRPCRequestSchema
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const requests = [
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'InitializeRequest',
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'PingRequest',
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'ListResourcesRequest',
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'ListResourceTemplatesRequest',
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'ReadResourceRequest',
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'SubscribeRequest',
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'UnsubscribeRequest',
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'ListPromptsRequest',
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'GetPromptRequest',
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'ListToolsRequest',
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'CallToolRequest',
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'GetTaskRequest',
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'ListTasksRequest',
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'GetTaskPayloadRequest',
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'CancelTaskRequest',
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'SetLevelRequest',
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'CreateMessageRequest',
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'CompleteRequest',
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'ListRootsRequest',
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'ElicitRequest',
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];
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// Replace JSONRPCNotificationSchema.extend with NotificationSchema.extend for specific schemas
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for (const name of notifications) {
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content = content.replace(
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new RegExp(`export const ${name}Schema = JSONRPCNotificationSchema\\.extend\\(`),
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`export const ${name}Schema = NotificationSchema.extend(`
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);
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}
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// Replace JSONRPCRequestSchema.extend with RequestSchema.extend for specific schemas
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for (const name of requests) {
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content = content.replace(
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new RegExp(`export const ${name}Schema = JSONRPCRequestSchema\\.extend\\(`),
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`export const ${name}Schema = RequestSchema.extend(`
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);
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}
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return content;
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}
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/**
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* Replace z.record(z.string(), z.unknown()).and(z.object({...})) with z.looseObject({...})
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* Uses brace-counting to handle nested objects correctly.
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*/
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function replaceRecordAndWithLooseObject(content: string): string {
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const pattern = 'z.record(z.string(), z.unknown()).and(z.object({';
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let result = content;
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let startIndex = 0;
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while (true) {
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const matchStart = result.indexOf(pattern, startIndex);
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if (matchStart === -1) break;
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// Find the matching closing brace for z.object({
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const objectStart = matchStart + pattern.length;
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let braceCount = 1;
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let i = objectStart;
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while (i < result.length && braceCount > 0) {
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if (result[i] === '{') braceCount++;
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else if (result[i] === '}') braceCount--;
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i++;
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}
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// i now points after the closing } of z.object({...})
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// Check if followed by ))
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if (result.slice(i, i + 2) === '))') {
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const objectContent = result.slice(objectStart, i - 1);
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const replacement = `z.looseObject({${objectContent}})`;
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result = result.slice(0, matchStart) + replacement + result.slice(i + 2);
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startIndex = matchStart + replacement.length;
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} else {
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startIndex = i;
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}
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}
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return result;
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}
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/**
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* Post-process generated integration tests.
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*/
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function postProcessTests(content: string): string {
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content = content.replace(
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'import { z } from "zod";',
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'import { z } from "zod/v4";',
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);
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content = content.replace(
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'// Generated by ts-to-zod',
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`// Generated by ts-to-zod
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// Integration tests verifying schemas match TypeScript types
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// Run: npm run generate:schemas`,
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);
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return content;
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}
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main().catch((error) => {
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console.error('❌ Schema generation failed:', error);
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process.exit(1);
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});

src/generated/index.ts

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/**
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* Generated Zod Schemas for MCP SDK
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*
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* This module provides auto-generated Zod schemas from spec.types.ts,
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* post-processed for SDK compatibility (extends Notification/Request
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* instead of JSONRPCNotification/JSONRPCRequest).
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*
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* The schemas here are designed to be drop-in replacements for the
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* manually-defined schemas in types.ts.
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*
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* @see spec.types.ts - MCP specification types
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* @see spec.schemas.ts - Auto-generated Zod schemas (SDK-compatible)
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* @see ../types.ts - Production schemas with SDK extras
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*/
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// Re-export all generated schemas (SDK-compatible hierarchy via post-processing)
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export * from './spec.schemas.js';
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// Re-export spec types
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export * from '../spec.types.js';
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// Re-export SDK version constants
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export { LATEST_PROTOCOL_VERSION, DEFAULT_NEGOTIATED_PROTOCOL_VERSION, SUPPORTED_PROTOCOL_VERSIONS, JSONRPC_VERSION } from '../types.js';

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