diff --git a/schemas/tags_schema.json b/schemas/tags_schema.json
new file mode 100644
index 000000000..aa12e8325
--- /dev/null
+++ b/schemas/tags_schema.json
@@ -0,0 +1,42 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "title": "Tags",
+  "description": "Maps each namespaced registry to its namespaced tags and their resolved, namespaced members. Nested #tag references are flattened by the generator, so members are always concrete entries.",
+  "type": "object",
+  "properties": {
+    "minecraft:block": {
+      "$ref": "#/$defs/tagMap",
+      "description": "Tags over the block registry (e.g. minecraft:mineable/pickaxe, minecraft:needs_iron_tool)."
+    },
+    "minecraft:item": {
+      "$ref": "#/$defs/tagMap",
+      "description": "Tags over the item registry (e.g. minecraft:pickaxes, minecraft:logs)."
+    }
+  },
+  "required": ["minecraft:block", "minecraft:item"],
+  "patternProperties": {
+    "^[a-z0-9_.-]+:[a-z0-9/._-]+$": {
+      "$ref": "#/$defs/tagMap",
+      "description": "Any additional namespaced registry the generator emits, including path-shaped registries such as minecraft:worldgen/biome."
+    }
+  },
+  "additionalProperties": false,
+  "$defs": {
+    "tagMap": {
+      "type": "object",
+      "minProperties": 1,
+      "description": "Maps a namespaced tag name to its resolved, namespaced member names. Empty member lists are valid because vanilla ships empty tags.",
+      "patternProperties": {
+        "^[a-z0-9_.-]+:[a-z0-9/._-]+$": {
+          "type": "array",
+          "items": {
+            "type": "string",
+            "pattern": "^[a-z0-9_.-]+:[a-z0-9/._-]+$"
+          },
+          "uniqueItems": true
+        }
+      },
+      "additionalProperties": false
+    }
+  }
+}
diff --git a/tools/js/test/audit_tags.js b/tools/js/test/audit_tags.js
new file mode 100644
index 000000000..f0dbd5b5d
--- /dev/null
+++ b/tools/js/test/audit_tags.js
@@ -0,0 +1,289 @@
+/* eslint-env mocha */
+
+const assert = require('assert')
+const fs = require('fs')
+const path = require('path')
+
+const root = path.join(__dirname, '../../..')
+const dataRoot = path.join(root, 'data')
+const pcDataRoot = path.join(dataRoot, 'pc')
+const dataPaths = require('../../../data/dataPaths.json')
+const registryFiles = {
+  'minecraft:block': 'blocks',
+  'minecraft:item': 'items',
+  'minecraft:entity_type': 'entities',
+  'minecraft:worldgen/biome': 'biomes',
+  'minecraft:enchantment': 'enchantments'
+}
+const resourceLocation = /^[a-z0-9_.-]+:[a-z0-9/._-]+$/
+
+function assertObject (value, label) {
+  assert(value && typeof value === 'object' && !Array.isArray(value), `${label} must be an object`)
+}
+
+function assertSorted (values, label) {
+  assert.deepStrictEqual(values, values.slice().sort(), `${label} must be sorted`)
+}
+
+function auditTagDocument (tags, options = {}) {
+  const label = options.label || 'tags.json'
+  const official = options.official || false
+  const registryMembers = options.registryMembers || {}
+
+  assertObject(tags, label)
+  const registries = Object.keys(tags)
+  assertSorted(registries, `${label} registry keys`)
+
+  for (const registry of registries) {
+    assert(resourceLocation.test(registry), `${label}: invalid registry ${registry}`)
+    if (official) assert(registry.startsWith('minecraft:'), `${label}: non-vanilla registry ${registry}`)
+    const tagMap = tags[registry]
+    assertObject(tagMap, `${label} ${registry}`)
+
+    const tagNames = Object.keys(tagMap)
+    assert(tagNames.length > 0, `${label} ${registry} must contain at least one named tag`)
+    assertSorted(tagNames, `${label} ${registry} tag keys`)
+
+    for (const tagName of tagNames) {
+      assert(resourceLocation.test(tagName), `${label}: invalid tag ${tagName}`)
+      if (official) assert(tagName.startsWith('minecraft:'), `${label}: non-vanilla tag ${tagName}`)
+      const members = tagMap[tagName]
+      assert(Array.isArray(members), `${label} ${tagName} must map to an array`)
+      assertSorted(members, `${label} ${tagName} members`)
+      assert.equal(new Set(members).size, members.length, `${label} ${tagName} has duplicate members`)
+
+      for (const member of members) {
+        assert.equal(typeof member, 'string', `${label} ${tagName} has a non-string member`)
+        assert(!member.startsWith('#'), `${label} ${tagName} contains unresolved tag ${member}`)
+        assert(resourceLocation.test(member), `${label} ${tagName} has invalid member ${member}`)
+        if (official) assert(member.startsWith('minecraft:'), `${label}: non-vanilla member ${member}`)
+        if (registryMembers[registry]) {
+          assert(registryMembers[registry].has(member), `${label} ${tagName} has dangling member ${member}`)
+        }
+      }
+    }
+  }
+
+  if (official) {
+    for (const required of ['minecraft:block', 'minecraft:item']) {
+      assert(Object.prototype.hasOwnProperty.call(tags, required),
+        `${label}: missing required registry ${required}`)
+    }
+  }
+}
+
+function namesForRegistry (dataPath, registry, label) {
+  const fileName = registryFiles[registry]
+  if (!fileName) return null
+
+  const target = dataPath[fileName]
+  assert(target, `${label}: missing ${fileName} dataPath for ${registry}`)
+  const file = path.join(dataRoot, target, fileName + '.json')
+  assert(fs.existsSync(file), `${label}: missing ${file}`)
+  const entries = JSON.parse(fs.readFileSync(file))
+  assert(Array.isArray(entries), `${label}: ${fileName}.json must be an array`)
+
+  return new Set(entries.map(entry => {
+    assert(entry && typeof entry.name === 'string', `${label}: ${fileName}.json entry has no name`)
+    return entry.name.includes(':') ? entry.name : 'minecraft:' + entry.name
+  }))
+}
+
+function findTagsFiles (dir, files = []) {
+  for (const entry of fs.readdirSync(dir, { withFileTypes: true })) {
+    const file = path.join(dir, entry.name)
+    if (entry.isDirectory()) {
+      findTagsFiles(file, files)
+    } else if (entry.name === 'tags.json') {
+      files.push(path.resolve(file))
+    }
+  }
+  return files
+}
+
+function getPcDataPaths (allDataPaths) {
+  return allDataPaths.pc || {}
+}
+
+describe('audit tags', function () {
+  it('keeps dataPaths and repository tags files consistent', function () {
+    const referenced = new Set()
+
+    for (const version in getPcDataPaths(dataPaths)) {
+      const dataPath = dataPaths.pc[version]
+      if (!dataPath.tags) continue
+
+      const label = `pc ${version}`
+      const tagsFile = path.resolve(dataRoot, dataPath.tags, 'tags.json')
+      assert(fs.existsSync(tagsFile), `${label}: missing ${tagsFile}`)
+      referenced.add(tagsFile)
+
+      const tags = JSON.parse(fs.readFileSync(tagsFile))
+      const registryMembers = {}
+      for (const registry of Object.keys(tags)) {
+        const names = namesForRegistry(dataPath, registry, label)
+        if (names) registryMembers[registry] = names
+      }
+      auditTagDocument(tags, { label, official: true, registryMembers })
+    }
+
+    for (const tagsFile of findTagsFiles(pcDataRoot)) {
+      assert(referenced.has(tagsFile), `tags file is not referenced by dataPaths: ${tagsFile}`)
+    }
+  })
+
+  it('does not apply the Java tag contract to non-PC data paths', function () {
+    const paths = getPcDataPaths({
+      pc: {},
+      bedrock: { future: { tags: 'bedrock/future' } }
+    })
+    assert.deepStrictEqual(paths, {})
+  })
+
+  function validTags () {
+    return {
+      'minecraft:block': {
+        'minecraft:mineable/axe': ['minecraft:oak_log'],
+        'minecraft:mineable/pickaxe': ['minecraft:granite', 'minecraft:stone']
+      },
+      'minecraft:fluid': {
+        'minecraft:water': ['minecraft:flowing_water', 'minecraft:water']
+      },
+      'minecraft:item': {
+        'minecraft:pickaxes': ['minecraft:diamond_pickaxe']
+      }
+    }
+  }
+
+  function members () {
+    return {
+      'minecraft:block': new Set(['minecraft:granite', 'minecraft:oak_log', 'minecraft:stone']),
+      'minecraft:item': new Set(['minecraft:diamond_pickaxe'])
+    }
+  }
+
+  it('accepts sorted data and structurally audits unmapped registries', function () {
+    auditTagDocument(validTags(), { official: true, registryMembers: members() })
+  })
+
+  it('rejects registries without named tags while preserving empty member arrays', function () {
+    const tags = validTags()
+    tags['minecraft:block'] = {}
+
+    assert.throws(
+      () => auditTagDocument(tags, { official: true }),
+      /must contain at least one named tag/
+    )
+
+    tags['minecraft:block'] = { 'minecraft:incorrect_for_diamond_tool': [] }
+    auditTagDocument(tags, { official: true })
+  })
+
+  it('audits PC artifacts for required block and item registries', function () {
+    const tags = validTags()
+    delete tags['minecraft:block']
+
+    assert.throws(
+      () => auditTagDocument(tags, { label: 'pc fixture', official: true }),
+      /missing required registry minecraft:block/
+    )
+  })
+
+  it('leaves the goat horn instrument registry structurally audited and unmapped', function () {
+    assert.equal(namesForRegistry({}, 'minecraft:instrument', 'test'), null)
+    const baseTags = validTags()
+    const tags = {
+      'minecraft:block': baseTags['minecraft:block'],
+      'minecraft:fluid': baseTags['minecraft:fluid'],
+      'minecraft:instrument': {
+        'minecraft:goat_horns': ['minecraft:ponder_goat_horn']
+      },
+      'minecraft:item': baseTags['minecraft:item']
+    }
+    auditTagDocument(tags, { official: true })
+  })
+
+  it('rejects malformed resource locations', function () {
+    assert.throws(
+      () => auditTagDocument({ 'minecraft:bad path': {} }),
+      /invalid registry/
+    )
+    assert.throws(
+      () => auditTagDocument({
+        'minecraft:block': { 'minecraft:bad path': [] }
+      }),
+      /invalid tag/
+    )
+    assert.throws(
+      () => auditTagDocument({
+        'minecraft:block': { 'minecraft:stone': ['minecraft:bad path'] }
+      }),
+      /invalid member/
+    )
+  })
+
+  it('rejects non-vanilla namespaces in official data', function () {
+    assert.throws(
+      () => auditTagDocument({ 'example:block': {} }, { official: true }),
+      /non-vanilla registry/
+    )
+    assert.throws(
+      () => auditTagDocument({
+        'minecraft:block': { 'example:mineable/pickaxe': [] }
+      }, { official: true }),
+      /non-vanilla tag/
+    )
+    assert.throws(
+      () => auditTagDocument({
+        'minecraft:block': { 'minecraft:mineable/pickaxe': ['example:stone'] }
+      }, { official: true }),
+      /non-vanilla member/
+    )
+  })
+
+  it('rejects unsorted registry keys', function () {
+    const tags = {
+      'minecraft:item': {},
+      'minecraft:block': {}
+    }
+    assert.throws(() => auditTagDocument(tags), /registry keys must be sorted/)
+  })
+
+  it('rejects unsorted tag keys', function () {
+    const tags = validTags()
+    tags['minecraft:block'] = {
+      'minecraft:mineable/pickaxe': ['minecraft:stone'],
+      'minecraft:mineable/axe': ['minecraft:oak_log']
+    }
+    assert.throws(() => auditTagDocument(tags), /tag keys must be sorted/)
+  })
+
+  it('rejects unsorted member arrays', function () {
+    const tags = validTags()
+    tags['minecraft:block']['minecraft:mineable/pickaxe'] = ['minecraft:stone', 'minecraft:granite']
+    assert.throws(() => auditTagDocument(tags), /members must be sorted/)
+  })
+
+  it('rejects duplicate members in PC tag documents', function () {
+    const tags = validTags()
+    tags['minecraft:block']['minecraft:mineable/pickaxe'] = ['minecraft:stone', 'minecraft:stone']
+    assert.throws(() => auditTagDocument(tags, { label: 'pc fixture', official: true }), /duplicate members/)
+  })
+
+  it('rejects unresolved tag members', function () {
+    const tags = validTags()
+    tags['minecraft:block']['minecraft:mineable/pickaxe'] = ['#minecraft:base_stone_overworld']
+    assert.throws(() => auditTagDocument(tags), /unresolved tag/)
+  })
+
+  it('rejects dangling members for mapped registries', function () {
+    const tags = validTags()
+    tags['minecraft:block']['minecraft:mineable/pickaxe'] = ['minecraft:andesite', 'minecraft:stone']
+    assert.throws(
+      () => auditTagDocument(tags, { registryMembers: members() }),
+      /dangling member minecraft:andesite/
+    )
+  })
+})
+
+module.exports = { auditTagDocument }
diff --git a/tools/js/test/tags_schema.js b/tools/js/test/tags_schema.js
new file mode 100644
index 000000000..7f5570cf4
--- /dev/null
+++ b/tools/js/test/tags_schema.js
@@ -0,0 +1,119 @@
+/* eslint-env mocha */
+
+const assert = require('assert')
+const Ajv = require('ajv')
+const schema = require('../../../schemas/tags_schema.json')
+
+function baseTags () {
+  return {
+    'minecraft:block': {
+      'minecraft:mineable/pickaxe': ['minecraft:granite', 'minecraft:stone']
+    },
+    'minecraft:item': {
+      'minecraft:pickaxes': ['minecraft:diamond_pickaxe']
+    }
+  }
+}
+
+function tagsWith (changes) {
+  return Object.assign(baseTags(), changes)
+}
+
+describe('tags schema', function () {
+  const validator = new Ajv({ verbose: true })
+
+  it('accepts namespaced registries, tags, and members', function () {
+    assert.ok(validator.validate(schema, baseTags()), JSON.stringify(validator.errors, null, 2))
+  })
+
+  it('accepts path-shaped registries, empty tags, and modded namespaces', function () {
+    const tags = baseTags()
+    tags['minecraft:block']['minecraft:incorrect_for_diamond_tool'] = []
+    tags['minecraft:worldgen/biome'] = {
+      'minecraft:is_overworld': ['minecraft:plains']
+    }
+    tags['example:block'] = {
+      'example:mineable/hammer': ['example:ore']
+    }
+    tags['minecraft:fluid'] = {
+      'minecraft:water': ['minecraft:flowing_water', 'minecraft:water']
+    }
+    tags['minecraft:entity_type'] = {
+      'minecraft:raiders': ['minecraft:pillager']
+    }
+    assert.ok(validator.validate(schema, tags), JSON.stringify(validator.errors, null, 2))
+  })
+
+  const invalid = [
+    {
+      name: 'missing required item registry',
+      value: { 'minecraft:block': { 'minecraft:logs': [] } }
+    },
+    {
+      name: 'missing required block registry',
+      value: { 'minecraft:item': { 'minecraft:pickaxes': [] } }
+    },
+    {
+      name: 'empty registry tag map',
+      value: tagsWith({ 'minecraft:block': {} })
+    },
+    {
+      name: 'registry without namespace',
+      value: tagsWith({ block: {} })
+    },
+    {
+      name: 'malformed registry namespace',
+      value: tagsWith({ 'mine craft:block': {} })
+    },
+    {
+      name: 'uppercase registry namespace',
+      value: tagsWith({ 'Minecraft:block': {} })
+    },
+    {
+      name: 'malformed registry path',
+      value: tagsWith({ 'minecraft:block path': {} })
+    },
+    {
+      name: 'tag without namespace',
+      value: tagsWith({ 'minecraft:block': { stone: [] } })
+    },
+    {
+      name: 'uppercase tag path',
+      value: tagsWith({ 'minecraft:block': { 'minecraft:Mineable/pickaxe': [] } })
+    },
+    {
+      name: 'member without namespace',
+      value: tagsWith({ 'minecraft:block': { 'minecraft:stone': ['stone'] } })
+    },
+    {
+      name: 'uppercase member path',
+      value: tagsWith({ 'minecraft:block': { 'minecraft:stone': ['minecraft:Stone'] } })
+    },
+    {
+      name: 'duplicate member',
+      value: tagsWith({ 'minecraft:block': { 'minecraft:stone': ['minecraft:stone', 'minecraft:stone'] } })
+    },
+    {
+      name: 'unresolved tag reference',
+      value: tagsWith({ 'minecraft:block': { 'minecraft:stone': ['#minecraft:base_stone_overworld'] } })
+    },
+    {
+      name: 'null registry',
+      value: tagsWith({ 'minecraft:block': null })
+    },
+    {
+      name: 'null tag members',
+      value: tagsWith({ 'minecraft:block': { 'minecraft:mineable/pickaxe': null } })
+    },
+    {
+      name: 'non-array tag members',
+      value: tagsWith({ 'minecraft:block': { 'minecraft:stone': 'minecraft:stone' } })
+    }
+  ]
+
+  for (const test of invalid) {
+    it('rejects ' + test.name, function () {
+      assert.equal(validator.validate(schema, test.value), false)
+    })
+  }
+})
diff --git a/tools/js/test/test.js b/tools/js/test/test.js
index 9b57ae421..a1005abda 100644
--- a/tools/js/test/test.js
+++ b/tools/js/test/test.js
@@ -18,7 +18,7 @@ after('the test suite stays fast', function () {
   assert.ok(ms < 40 * 1000, `the test suite took ${Math.round(ms)}ms, expected < 40s`)
 })
 
-const data = ['attributes', 'biomes', 'commands', 'instruments', 'items', 'materials', 'blocks', 'blockCollisionShapes', 'recipes', 'windows', 'entities', 'protocol', 'version', 'effects', 'enchantments', 'language', 'foods', 'particles', 'blockLoot', 'entityLoot', 'mapIcons', 'tints', 'blockMappings', 'sounds', 'blockStates']
+const data = ['attributes', 'biomes', 'commands', 'instruments', 'items', 'materials', 'blocks', 'blockCollisionShapes', 'recipes', 'windows', 'entities', 'protocol', 'version', 'effects', 'enchantments', 'language', 'foods', 'particles', 'blockLoot', 'entityLoot', 'mapIcons', 'tints', 'blockMappings', 'sounds', 'blockStates', 'tags']
 
 require('./version_iterator')(function (p, versionString) {
   describe('minecraft-data schemas ' + versionString, function () {