diff --git a/packages/mds-policy-linter/LICENSE b/packages/mds-policy-linter/LICENSE
new file mode 100644
index 000000000..261eeb9e9
--- /dev/null
+++ b/packages/mds-policy-linter/LICENSE
@@ -0,0 +1,201 @@
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diff --git a/packages/mds-policy-linter/README.md b/packages/mds-policy-linter/README.md
new file mode 100644
index 000000000..58efc0ddf
--- /dev/null
+++ b/packages/mds-policy-linter/README.md
@@ -0,0 +1,21 @@
+# MDS Policy Linter CLI
+
+Validation tool for [MDS-Policy](https://github.com/openmobilityfoundation/mobility-data-specification/blob/dev/policy/README.md) documents.
+
+## Package Content
+
+### Stable Content
+
+This package contains an MDS-Policy 1.0.0 implementation
+
+### Experimental Content
+
+So far, everything, lolz.
+
+## Quick Start and Tests
+
+See [Quick Start](../../README.md#Installation)
+
+## Build Deployment Package
+
+See [Build](../../README.md#Build)
diff --git a/packages/mds-policy-linter/index.ts b/packages/mds-policy-linter/index.ts
new file mode 100755
index 000000000..6c1ca1763
--- /dev/null
+++ b/packages/mds-policy-linter/index.ts
@@ -0,0 +1,128 @@
+#!/usr/local/bin/node
+/**
+ * Copyright 2022 City of Los Angeles
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { PolicyDomainCreateModel, validatePolicyDomainModel } from '@mds-core/mds-policy-service'
+import { readFileSync } from 'fs'
+import { describePolicy, invalidDate, num, plural, shortDate, validDate } from './utils'
+// import yargs from 'yargs/yargs'
+
+const args = process.argv.slice(2)
+// const argv = yargs(args).usage('Usage: [options] [files]').help('h').alias('h', 'help').options({
+//   // TODO options
+// }).argv
+
+const { log } = console
+
+// TODO use yargs correctly
+log(`mds-policy-linter reading ${plural(args.length, 'files')}`)
+
+// the list of policies that make it past the validator
+const validPolicies: PolicyDomainCreateModel[] = []
+
+const validPolicyMap: { [key: string]: PolicyDomainCreateModel } = {}
+
+interface LinterRule {
+  name: string
+  func: RuleFunction
+}
+
+const lintRules: LinterRule[] = []
+
+// realistically I could use globals for the list of policies but that feels weird
+interface RuleFunction {
+  (policies: PolicyDomainCreateModel[]): void
+}
+
+function addRule(name: string, func: RuleFunction) {
+  lintRules.push({ name, func })
+}
+
+addRule('check for publish_date', (policies: PolicyDomainCreateModel[]) => {
+  policies.forEach(policy => {
+    let reason
+    if ((reason = invalidDate(policy.publish_date))) {
+      log(describePolicy(policy), `does not have a valid publish_date (${policy.publish_date} is ${reason})`)
+    }
+  })
+})
+
+addRule('retroactive start date', (policies: PolicyDomainCreateModel[]) => {
+  policies.forEach(policy => {
+    if (validDate(policy.start_date) && validDate(policy.publish_date)) {
+      if (policy.start_date >= num(policy.publish_date)) {
+        log(describePolicy(policy), 'has a start_date prior to its publish_date')
+      }
+    }
+  })
+})
+
+addRule('invalid prev_policy', (policies: PolicyDomainCreateModel[]) => {
+  policies.forEach(policy => {
+    const pp_ids: string[] = policy.prev_policies || []
+    pp_ids.forEach(pp_id => {
+      const prev_policy: PolicyDomainCreateModel | undefined = validPolicyMap[pp_id]
+      if (prev_policy === undefined) {
+        // if there's a prev_policy, it must point to a known policy
+        log(describePolicy(policy), `contains prev_policy ${pp_id} which was not found in the input file(s)`)
+      } else if (policy.start_date < prev_policy.start_date) {
+        // if there's a prev_policy, it (usually) shouldn't be effective before the original policy's start_date
+        log(
+          describePolicy(policy),
+          `has a start date (${shortDate(policy.start_date)}) ` +
+            `prior to its previous policy's start date (${shortDate(prev_policy.start_date)})`
+        )
+      }
+    })
+  })
+})
+
+// read files
+args.forEach(fn => {
+  try {
+    const json: string = readFileSync(fn, { encoding: 'utf8' })
+    const parsed: { policies: object[] } = JSON.parse(json)
+    const policiesRaw: object[] = parsed.policies ? parsed.policies : [parsed]
+    policiesRaw.forEach(policyRaw => {
+      try {
+        const validPolicy: PolicyDomainCreateModel = validatePolicyDomainModel(policyRaw)
+        validPolicies.push(validPolicy)
+      } catch (e) {
+        log(`error in ${JSON.stringify(policyRaw)}: ${e}`)
+      }
+    })
+  } catch (e) {
+    log(`error in ${fn}: ${e}`)
+  }
+})
+
+validPolicies.forEach(policy => (validPolicyMap[policy.policy_id] = policy))
+
+log(`read ${plural(validPolicies.length, 'valid policies')}`)
+
+validPolicies.forEach(p => {
+  log(`${p.name} has ${plural(p.rules.length, 'rules')}`)
+})
+
+lintRules.forEach(lintRule => {
+  lintRule.func(validPolicies)
+})
+
+// run heuristics:
+// * date/time constraints e.g. can't publish retroactive Policy
+// * more than one obsoleting function
+// * show effective policies for arbitrary date/time
+// * compute metadata e.g. when a policy becomes deprecated
diff --git a/packages/mds-policy-linter/package.json b/packages/mds-policy-linter/package.json
new file mode 100644
index 000000000..87b461bf4
--- /dev/null
+++ b/packages/mds-policy-linter/package.json
@@ -0,0 +1,26 @@
+{
+  "name": "@mds-core/mds-policy-linter",
+  "version": "0.1.0",
+  "description": "Linter tool for MDS Policy documents",
+  "keywords": [
+    "policy",
+    "lint"
+  ],
+  "license": "Apache-2.0",
+  "author": "Marie Maxham",
+  "main": "dist/index.js",
+  "types": "dist/index.d.ts",
+  "scripts": {
+    "build": "tsc --build tsconfig.build.json",
+    "start": "pnpm watch index.ts",
+    "test": "echo \"Error: no test specified\" && exit 1",
+    "watch": "pnpm build && nodemon --watch '../../packages' --ext 'ts' --ignore '*.d.ts' --exec pnpm ts-node --"
+  },
+  "dependencies": {
+    "@mds-core/mds-policy-service": "workspace:0.11.26",
+    "@mds-core/mds-types": "workspace:0.9.2",
+    "@mds-core/mds-utils": "workspace:0.5.0",
+    "ajv": "8.10.0",
+    "yargs": "17.3.1"
+  }
+}
diff --git a/packages/mds-policy-linter/test_data/bogus-start-date.json b/packages/mds-policy-linter/test_data/bogus-start-date.json
new file mode 100644
index 000000000..29763fa4d
--- /dev/null
+++ b/packages/mds-policy-linter/test_data/bogus-start-date.json
@@ -0,0 +1,11 @@
+{
+  "policies": [{
+    "policy_id": "bbf89fce-b50f-4aa7-9dc4-7c66a76038e7",
+    "currency": "USD",
+    "name": "Empty Policy",
+    "description": "Empty Policy",
+    "start_date": -1,
+    "end_date": null,
+    "rules": []
+  }]
+}
\ No newline at end of file
diff --git a/packages/mds-policy-linter/test_data/empty.json b/packages/mds-policy-linter/test_data/empty.json
new file mode 100644
index 000000000..3ada539e0
--- /dev/null
+++ b/packages/mds-policy-linter/test_data/empty.json
@@ -0,0 +1 @@
+{ "policies": [] }
\ No newline at end of file
diff --git a/packages/mds-policy-linter/test_data/idle-time.json b/packages/mds-policy-linter/test_data/idle-time.json
new file mode 100644
index 000000000..f49247e2c
--- /dev/null
+++ b/packages/mds-policy-linter/test_data/idle-time.json
@@ -0,0 +1,47 @@
+{
+  "policy_id": "a2c9a65f-fd85-463e-9564-fc95ea473f7d",
+  "name": "Idle Times",
+  "description": "LADOT Idle Time Limitations",
+  "start_date": 1552678594428,
+  "end_date": null,
+  "published_date": 1558389669540,
+  "prev_policies": null,
+  "rules": [
+    {
+      "name": "Greater LA (rentable)",
+      "rule_id": "e1942f2d-e5c7-46c4-94c7-293d4e481ed0",
+      "rule_type": "time",
+      "rule_units": "hours",
+      "geographies": [
+        "b4bcc213-4888-48ce-a33d-4dd6c3384bda"
+      ],
+      "states": {
+        "available": [],
+        "reserved": []
+      },
+      "vehicle_types": [
+        "bicycle",
+        "scooter"
+      ],
+      "maximum": 72
+    },
+    {
+      "name": "Greater LA (non-rentable)",
+      "rule_id": "a7eb28b9-969e-4c52-b18c-4243a96f7143",
+      "rule_type": "time",
+      "rule_units": "hours",
+      "geographies": [
+        "12b3fcf5-22af-4b0d-a169-ac7ac903d3b9"
+      ],
+      "states": {
+        "non_operational": [],
+        "on_trip": []
+      },
+      "vehicle_types": [
+        "bicycle",
+        "scooter"
+      ],
+      "maximum": 24
+    }
+  ]
+}
diff --git a/packages/mds-policy-linter/test_data/missing-name.json b/packages/mds-policy-linter/test_data/missing-name.json
new file mode 100644
index 000000000..83bb19f63
--- /dev/null
+++ b/packages/mds-policy-linter/test_data/missing-name.json
@@ -0,0 +1,11 @@
+{
+  "policies": [{
+    "policy_id": "bbf89fce-b50f-4aa7-9dc4-7c66a76038e7",
+    "currency": "USD",
+    "description": "Empty Policy",
+    "start_date": 1646871890724,
+    "end_date": null,
+    "rules": []
+  }]
+}
+
diff --git a/packages/mds-policy-linter/test_data/one-empty-policy.json b/packages/mds-policy-linter/test_data/one-empty-policy.json
new file mode 100644
index 000000000..2351428ff
--- /dev/null
+++ b/packages/mds-policy-linter/test_data/one-empty-policy.json
@@ -0,0 +1,11 @@
+{
+  "policies": [{
+    "policy_id": "bbf89fce-b50f-4aa7-9dc4-7c66a76038e7",
+    "currency": "USD",
+    "name": "Empty Policy",
+    "description": "Empty Policy",
+    "start_date": 1646871890724,
+    "end_date": null,
+    "rules": []
+  }]
+}
\ No newline at end of file
diff --git a/packages/mds-policy-linter/test_data/prohibted-zone.json b/packages/mds-policy-linter/test_data/prohibted-zone.json
new file mode 100644
index 000000000..06e8d5102
--- /dev/null
+++ b/packages/mds-policy-linter/test_data/prohibted-zone.json
@@ -0,0 +1,32 @@
+{
+  "policy_id": "39a653be-7180-4188-b1a6-cae33c280341",
+  "name": "Prohibited Dockless Zones",
+  "description": "Prohibited areas for dockless vehicles within the City of Los Angeles for the LADOT Dockless On-Demand Personal Mobility Program",
+  "provider_ids": null,
+  "start_date": 1552678594428,
+  "end_date": null,
+  "published_date": 1552678594428,
+  "prev_policies": null,
+  "rules": [
+    {
+      "name": "Prohibited Dockless Zones",
+      "rule_id": "8ad39dc3-005b-4348-9d61-c830c54c161b",
+      "rule_type": "count",
+      "rule_units": "devices",
+      "geographies": [
+        "c0591267-bb6a-4f28-a612-ff7f4a8f8b2a"
+      ],
+      "states": {
+        "available": [],
+        "non_operational": [],
+        "reserved": [],
+        "on_trip": []
+      },
+      "vehicle_types": [
+        "bicycle",
+        "scooter"
+      ],
+      "maximum": 0
+    }
+  ]
+}
diff --git a/packages/mds-policy-linter/test_data/provider-cap.json b/packages/mds-policy-linter/test_data/provider-cap.json
new file mode 100644
index 000000000..7ac1f30e1
--- /dev/null
+++ b/packages/mds-policy-linter/test_data/provider-cap.json
@@ -0,0 +1,55 @@
+{
+  "name": "Test City Mobility Caps: Company X",
+  "description": "Mobility caps as described in the One-Year Permit",
+  "policy_id": "99f7a469-6e3a-4981-9313-c2f6c0bbd5ce",
+  "provider_ids": [
+    "2411d395-04f2-47c9-ab66-d09e9e3c3251"
+  ],
+  "start_date": 1558389669540,
+  "end_date": null,
+  "published_date": 1558389669540,
+  "prev_policies": null,
+  "rules": [
+    {
+      "name": "Disadvantaged Community",
+      "rule_id": "8a61de66-d9fa-4cba-a38d-5d948e2373fe",
+      "rule_type": "count",
+      "rule_units": "devices",
+      "geographies": [
+        "e3ed0a0e-61d3-4887-8b6a-4af4f3769c14"
+      ],
+      "states": {
+        "available": [],
+        "non_operational": [],
+        "reserved": [],
+        "on_trip": []
+      },
+      "vehicle_types": [
+        "bicycle",
+        "scooter"
+      ],
+      "maximum": 10000
+    },
+    {
+      "name": "Not Disadvantaged Communities",
+      "rule_id": "57d47e74-6aef-4f41-b0c5-79bb35aa5b9d",
+      "rule_type": "count",
+      "rule_units": "devices",
+      "geographies": [
+        "1f943d59-ccc9-4d91-b6e2-0c5e771cbc49"
+      ],
+      "states": {
+        "available": [],
+        "non_operational": [],
+        "reserved": [],
+        "on_trip": []
+      },
+      "vehicle_types": [
+        "bicycle",
+        "scooter"
+      ],
+      "maximum": 3000
+    }
+  ]
+}
+
diff --git a/packages/mds-policy-linter/test_data/required-parking.json b/packages/mds-policy-linter/test_data/required-parking.json
new file mode 100644
index 000000000..53b0215a1
--- /dev/null
+++ b/packages/mds-policy-linter/test_data/required-parking.json
@@ -0,0 +1,50 @@
+{
+  "policy_id": "99f7a469-6e3a-4981-9313-c2f6c0bbd5ce",
+  "name": "Test City Mobility Hubs",
+  "description": "Enforced parking in specific mobility hubs for downtown area",
+  "start_date": 1558389669540,
+  "end_date": null,
+  "published_date": 1558389669540,
+  "prev_policies": null,
+  "rules": [
+    {
+      "name": "Allow parking in specific locations",
+      "rule_id": "8a61de66-d9fa-4cba-a38d-5d948e2373fe",
+      "minimum": 0,
+      "rule_type": "count",
+      "rule_units": "devices",
+      "geographies": [
+        "e3ed0a0e-61d3-4887-8b6a-4af4f3769c14",
+        "1512a3f4-313c-45fc-9fae-0dca6d7ab355"
+      ],
+      "states": {
+        "available": [
+          "trip_end"
+        ]
+      },
+      "vehicle_types": [
+        "bicycle",
+        "scooter"
+      ]
+    },
+    {
+      "name": "Disallow parking elsewhere in downtown area",
+      "rule_id": "0240899e-a8ad-4263-953a-6e278ff859ab",
+      "rule_type": "count",
+      "maximum": 0,
+      "rule_units": "devices",
+      "geographies": [
+        "075a5303-2571-4ca5-b429-841bcc4025d1"
+      ],
+      "states": {
+        "available": [
+          "trip_end"
+        ]
+      },
+      "vehicle_types": [
+        "bicycle",
+        "scooter"
+      ]
+    }
+  ]
+}
diff --git a/packages/mds-policy-linter/tests/fixtures.ts b/packages/mds-policy-linter/tests/fixtures.ts
new file mode 100644
index 000000000..dcbee589c
--- /dev/null
+++ b/packages/mds-policy-linter/tests/fixtures.ts
@@ -0,0 +1,60 @@
+// TODO copyright
+// TODO this is copypasta
+
+import { PolicyDomainModel } from '@mds-core/mds-policy-service'
+import { days } from '@mds-core/mds-utils'
+
+export const TIME = 1605821758034
+export const POLICY_ID_1 = '6d7a9c7e-853c-4ff7-a86f-e17c06d3bd80'
+export const POLICY_ID_2 = 'dfe3f757-c43a-4eb6-b85e-abc00f3e8387'
+export const PROVIDER_ID_1 = 'c20e08cf-8488-46a6-a66c-5d8fb827f7e0'
+export const PROVIDER_ID_2 = '63f13c48-34ff-49d2-aca7-cf6a5b6171c3'
+const GEOGRAPHY_UUID = '1f943d59-ccc9-4d91-b6e2-0c5e771cbc49'
+
+export const POLICY1: PolicyDomainModel = {
+  name: 'Policy 1',
+  description: 'Mobility caps as described in the One-Year Permit',
+  policy_id: POLICY_ID_1,
+  start_date: TIME - days(30),
+  end_date: null,
+  publish_date: TIME - days(30),
+  prev_policies: null,
+  currency: null,
+  provider_ids: [],
+  rules: [
+    {
+      rule_type: 'count',
+      rule_id: '7ea0d16e-ad15-4337-9722-9924e3af9146',
+      name: 'Greater LA',
+      geographies: [GEOGRAPHY_UUID],
+      states: { available: [], removed: [], reserved: [], on_trip: [] },
+      vehicle_types: ['bicycle', 'scooter'],
+      maximum: 3000,
+      minimum: 500
+    }
+  ]
+}
+
+export const POLICY2: PolicyDomainModel = {
+  name: 'Policy 2',
+  description: 'Mobility caps as described in the One-Year Permit',
+  policy_id: POLICY_ID_2,
+  start_date: TIME - days(30),
+  end_date: null,
+  publish_date: TIME - days(30),
+  prev_policies: null,
+  currency: null,
+  provider_ids: [],
+  rules: [
+    {
+      rule_type: 'count',
+      rule_id: 'c29bff02-b260-4dfa-b7de-4b9a38a74cd9',
+      name: 'Greater LA',
+      geographies: [GEOGRAPHY_UUID],
+      states: { available: [], removed: [], reserved: [], on_trip: [] },
+      vehicle_types: ['bicycle', 'scooter'],
+      maximum: 3000,
+      minimum: 500
+    }
+  ]
+}
diff --git a/packages/mds-policy-linter/tsconfig.build.json b/packages/mds-policy-linter/tsconfig.build.json
new file mode 100644
index 000000000..c568fe37f
--- /dev/null
+++ b/packages/mds-policy-linter/tsconfig.build.json
@@ -0,0 +1,11 @@
+{
+  "extends": "../../tsconfig.build.json",
+  "compilerOptions": {
+    "outDir": "dist"
+  },
+  "references": [
+   { "path": "../../packages/mds-policy-service/tsconfig.build.json" },
+   { "path": "../../packages/mds-types/tsconfig.build.json" },
+   { "path": "../../packages/mds-utils/tsconfig.build.json" }
+  ]
+}
diff --git a/packages/mds-policy-linter/utils.ts b/packages/mds-policy-linter/utils.ts
new file mode 100644
index 000000000..9f212fd37
--- /dev/null
+++ b/packages/mds-policy-linter/utils.ts
@@ -0,0 +1,60 @@
+// Copyright 2022 City of Los Angeles
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import { PolicyDomainCreateModel } from '@mds-core/mds-policy-service'
+import { Nullable } from '@mds-core/mds-types'
+
+function describePolicy(policy: PolicyDomainCreateModel): string {
+  return policy.name + ' (' + policy.policy_id + ')'
+}
+
+const JAN_2020 = new Date(2020, 1, 1).getDate()
+/**
+ * is a date invalid?
+ * @param t a number or null or undefined
+ * @returns a string describing why a date is not legit, null for 'legit'
+ */
+function invalidDate(t: Nullable<number> | undefined): string | null {
+  if (typeof t !== 'number') {
+    return 'not a number'
+  }
+  if (t < JAN_2020) {
+    return 'too early'
+  }
+  return null
+}
+
+/**
+ * is a date valid?
+ * @param t a number or null or undefined
+ * @returns is the date valid, true or false
+ */
+function validDate(t: Nullable<number> | undefined): boolean {
+  return invalidDate(t) === null
+}
+
+function plural(n: number, s: string): string {
+  return '' + n + ' ' + (n === 1 ? s.replace(/ies$/, 'y').replace(/s$/, '') : s)
+}
+
+// IDK if this is the best way to get the compiler to shut up or what ...
+function num(n: Nullable<number> | undefined) {
+  return n || 0
+}
+
+function shortDate(n: number): string {
+  return new Date(n).toLocaleString()
+}
+
+export { describePolicy, invalidDate, validDate, plural, num, shortDate }
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 483dbc186..d8bc92267 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -1223,6 +1223,20 @@ importers:
       '@mds-core/mds-stream': link:../mds-stream
       '@mds-core/mds-test-data': link:../mds-test-data
 
+  packages/mds-policy-linter:
+    specifiers:
+      '@mds-core/mds-policy-service': workspace:0.11.26
+      '@mds-core/mds-types': workspace:0.9.2
+      '@mds-core/mds-utils': workspace:0.5.0
+      ajv: 8.10.0
+      yargs: 17.3.1
+    dependencies:
+      '@mds-core/mds-policy-service': link:../mds-policy-service
+      '@mds-core/mds-types': link:../mds-types
+      '@mds-core/mds-utils': link:../mds-utils
+      ajv: 8.10.0
+      yargs: 17.3.1
+
   packages/mds-policy-service:
     specifiers:
       '@mds-core/mds-geography-service': workspace:0.10.20
@@ -3584,6 +3598,15 @@ packages:
       uri-js: 4.4.1
     dev: true
 
+  /ajv/8.10.0:
+    resolution: {integrity: sha512-bzqAEZOjkrUMl2afH8dknrq5KEk2SrwdBROR+vH1EKVQTqaUbJVPdc/gEdggTMM0Se+s+Ja4ju4TlNcStKl2Hw==}
+    dependencies:
+      fast-deep-equal: 3.1.3
+      json-schema-traverse: 1.0.0
+      require-from-string: 2.0.2
+      uri-js: 4.4.1
+    dev: false
+
   /ajv/8.6.3:
     resolution: {integrity: sha512-SMJOdDP6LqTkD0Uq8qLi+gMwSt0imXLSV080qFVwJCpH9U6Mb+SUGHAXM0KNbcBPguytWyvFxcHgMLe2D2XSpw==}
     dependencies: