diff --git a/README.md b/README.md
index bf9d2df..0b7ca65 100644
--- a/README.md
+++ b/README.md
@@ -114,6 +114,57 @@ rootly.com/catalog-slug: customer-tier # Alternative to catalog-id. The catalog
 rootly.com/catalog-description: Customer pricing tiers # Optional. Description for the catalog when auto-creating.
 ```
 
+#### Attribute pass-through annotations
+
+You can set any Rootly API attribute on services, functionalities, teams, and catalog entities using the `attr` prefix:
+
+```yaml
+rootly.com/service-attr-<api_attribute>: "value"
+rootly.com/functionality-attr-<api_attribute>: "value"
+rootly.com/team-attr-<api_attribute>: "value"
+rootly.com/catalog-entity-attr-<api_attribute>: "value"
+```
+
+Value coercion rules:
+- `"true"` / `"false"` → boolean
+- Values starting with `[` or `{` → parsed as JSON (arrays, objects)
+- Everything else → plain string
+
+Example:
+
+```yaml
+annotations:
+  rootly.com/service-slug: my-service
+  rootly.com/service-auto-import: enabled
+  rootly.com/service-attr-color: "#FF5733"
+  rootly.com/service-attr-notify_emails: '["oncall@company.com","team@company.com"]'
+  rootly.com/service-attr-slack_channels: '[{"id":"C01ABC123","name":"oncall-channel"}]'
+  rootly.com/service-attr-show_uptime: "true"
+  rootly.com/service-attr-github_repository_name: "myorg/my-service"
+```
+
+Hardcoded fields (`name`, `description`, `backstage_id`, `pagerduty_id`, `owner_group_ids`) always take precedence and cannot be overridden via pass-through annotations.
+
+#### Custom catalog property annotations
+
+You can populate custom catalog properties (metadata fields) on services and catalog entities:
+
+```yaml
+rootly.com/service-property-<slug_or_id>: "value"
+rootly.com/catalog-entity-property-<slug_or_id>: "value"
+```
+
+The key after the prefix is the catalog property slug or UUID. The value is passed as-is to the Rootly API.
+
+Example:
+
+```yaml
+annotations:
+  rootly.com/service-slug: my-service
+  rootly.com/service-property-impact-level: "critical"
+  rootly.com/service-property-slack-channel: '{"id":"C01FE4P7458","name":"service-channel"}'
+```
+
 #### Example
 
 ```yaml
diff --git a/src/api.test.ts b/src/api.test.ts
new file mode 100644
index 0000000..ea899cc
--- /dev/null
+++ b/src/api.test.ts
@@ -0,0 +1,155 @@
+import { extractPassthroughAttributes, extractProperties } from './api';
+
+describe('extractPassthroughAttributes', () => {
+  const prefix = 'rootly.com/service-attr-';
+
+  it('returns empty object when annotations is undefined', () => {
+    expect(extractPassthroughAttributes(undefined, prefix)).toEqual({});
+  });
+
+  it('returns empty object when no annotations match prefix', () => {
+    const annotations = {
+      'rootly.com/service-id': '123',
+      'pagerduty.com/service-id': 'PD123',
+    };
+    expect(extractPassthroughAttributes(annotations, prefix)).toEqual({});
+  });
+
+  it('passes through simple string values', () => {
+    const annotations = {
+      'rootly.com/service-attr-color': '#FF5733',
+      'rootly.com/service-attr-github_repository_name': 'rootlyhq/my-service',
+    };
+    expect(extractPassthroughAttributes(annotations, prefix)).toEqual({
+      color: '#FF5733',
+      github_repository_name: 'rootlyhq/my-service',
+    });
+  });
+
+  it('coerces "true" and "false" to booleans', () => {
+    const annotations = {
+      'rootly.com/service-attr-show_uptime': 'true',
+      'rootly.com/service-attr-alert_broadcast_enabled': 'false',
+    };
+    expect(extractPassthroughAttributes(annotations, prefix)).toEqual({
+      show_uptime: true,
+      alert_broadcast_enabled: false,
+    });
+  });
+
+  it('parses JSON arrays', () => {
+    const annotations = {
+      'rootly.com/service-attr-notify_emails': '["alice@co.com","bob@co.com"]',
+    };
+    expect(extractPassthroughAttributes(annotations, prefix)).toEqual({
+      notify_emails: ['alice@co.com', 'bob@co.com'],
+    });
+  });
+
+  it('parses JSON objects', () => {
+    const annotations = {
+      'rootly.com/service-attr-slack_channels': '[{"id":"C01ABC","name":"oncall"}]',
+    };
+    expect(extractPassthroughAttributes(annotations, prefix)).toEqual({
+      slack_channels: [{ id: 'C01ABC', name: 'oncall' }],
+    });
+  });
+
+  it('falls back to string on invalid JSON', () => {
+    const annotations = {
+      'rootly.com/service-attr-bad_json': '{not valid json',
+    };
+    expect(extractPassthroughAttributes(annotations, prefix)).toEqual({
+      bad_json: '{not valid json',
+    });
+  });
+
+  it('ignores empty attribute name after prefix', () => {
+    const annotations = {
+      'rootly.com/service-attr-': 'value',
+    };
+    expect(extractPassthroughAttributes(annotations, prefix)).toEqual({});
+  });
+
+  it('handles mixed matching and non-matching annotations', () => {
+    const annotations = {
+      'rootly.com/service-id': '123',
+      'rootly.com/service-attr-color': '#000',
+      'rootly.com/functionality-attr-color': '#FFF',
+      'rootly.com/service-attr-show_uptime': 'true',
+    };
+    expect(extractPassthroughAttributes(annotations, prefix)).toEqual({
+      color: '#000',
+      show_uptime: true,
+    });
+  });
+
+  it('works with different prefixes', () => {
+    const annotations = {
+      'rootly.com/team-attr-color': 'blue',
+    };
+    expect(extractPassthroughAttributes(annotations, 'rootly.com/team-attr-')).toEqual({
+      color: 'blue',
+    });
+  });
+});
+
+describe('extractProperties', () => {
+  const prefix = 'rootly.com/service-property-';
+
+  it('returns empty array when annotations is undefined', () => {
+    expect(extractProperties(undefined, prefix)).toEqual([]);
+  });
+
+  it('returns empty array when no annotations match prefix', () => {
+    const annotations = {
+      'rootly.com/service-id': '123',
+    };
+    expect(extractProperties(annotations, prefix)).toEqual([]);
+  });
+
+  it('extracts properties with slug keys', () => {
+    const annotations = {
+      'rootly.com/service-property-my-custom-field': 'hello',
+    };
+    expect(extractProperties(annotations, prefix)).toEqual([
+      { catalog_property_id: 'my-custom-field', value: 'hello' },
+    ]);
+  });
+
+  it('extracts properties with UUID keys', () => {
+    const annotations = {
+      'rootly.com/service-property-dcece7f7-b73c-4f32-8b09-695abad42e60': 'world',
+    };
+    expect(extractProperties(annotations, prefix)).toEqual([
+      { catalog_property_id: 'dcece7f7-b73c-4f32-8b09-695abad42e60', value: 'world' },
+    ]);
+  });
+
+  it('keeps value as raw string (no coercion)', () => {
+    const annotations = {
+      'rootly.com/service-property-slack-channel': '{"id":"C01FE4P7458","name":"oncall"}',
+    };
+    expect(extractProperties(annotations, prefix)).toEqual([
+      { catalog_property_id: 'slack-channel', value: '{"id":"C01FE4P7458","name":"oncall"}' },
+    ]);
+  });
+
+  it('extracts multiple properties', () => {
+    const annotations = {
+      'rootly.com/service-property-field-a': 'val1',
+      'rootly.com/service-property-field-b': 'val2',
+    };
+    const result = extractProperties(annotations, prefix);
+    expect(result).toHaveLength(2);
+    expect(result).toContainEqual({ catalog_property_id: 'field-a', value: 'val1' });
+    expect(result).toContainEqual({ catalog_property_id: 'field-b', value: 'val2' });
+  });
+
+  it('ignores empty property id after prefix', () => {
+    const annotations = {
+      'rootly.com/service-property-': 'value',
+    };
+    expect(extractProperties(annotations, prefix)).toEqual([]);
+  });
+});
diff --git a/src/api.ts b/src/api.ts
index aacbd85..56a6601 100644
--- a/src/api.ts
+++ b/src/api.ts
@@ -14,6 +14,12 @@ import {
   ROOTLY_ANNOTATION_TEAM_NAME,
   ROOTLY_ANNOTATION_SERVICE_NAME,
   ROOTLY_ANNOTATION_CATALOG_ENTITY_NAME,
+  ROOTLY_ANNOTATION_SERVICE_ATTR_PREFIX,
+  ROOTLY_ANNOTATION_SERVICE_PROPERTY_PREFIX,
+  ROOTLY_ANNOTATION_FUNCTIONALITY_ATTR_PREFIX,
+  ROOTLY_ANNOTATION_TEAM_ATTR_PREFIX,
+  ROOTLY_ANNOTATION_CATALOG_ENTITY_ATTR_PREFIX,
+  ROOTLY_ANNOTATION_CATALOG_ENTITY_PROPERTY_PREFIX,
 } from './constants';
 
 export type RootlyServicesFetchOpts = {
@@ -236,6 +242,50 @@ export interface RootlyCatalogEntitiesResponse {
   data: RootlyCatalogEntity[];
 }
 
+function extractAnnotationEntries(
+  annotations: Record<string, string> | undefined,
+  prefix: string,
+): Array<[string, string]> {
+  if (!annotations) return [];
+  return Object.entries(annotations)
+    .filter(([k]) => k.startsWith(prefix))
+    .map(([k, v]) => [k.slice(prefix.length), v])
+    .filter(([k]) => k !== '');
+}
+
+function coerceAnnotationValue(value: string): unknown {
+  if (value === 'true') return true;
+  if (value === 'false') return false;
+  if ((value.startsWith('[') || value.startsWith('{')) && value.length > 1) {
+    try {
+      return JSON.parse(value);
+    } catch {
+      return value;
+    }
+  }
+  return value;
+}
+
+/** @public */
+export function extractPassthroughAttributes(
+  annotations: Record<string, string> | undefined,
+  prefix: string,
+): Record<string, unknown> {
+  return Object.fromEntries(
+    extractAnnotationEntries(annotations, prefix).map(([k, v]) => [k, coerceAnnotationValue(v)]),
+  );
+}
+
+/** @public */
+export function extractProperties(
+  annotations: Record<string, string> | undefined,
+  prefix: string,
+): Array<{ catalog_property_id: string; value: string }> {
+  return extractAnnotationEntries(annotations, prefix).map(([k, v]) => ({
+    catalog_property_id: k, value: v,
+  }));
+}
+
 const DEFAULT_PROXY_PATH = '/rootly/api';
 
 type Options = {
@@ -483,6 +533,8 @@ export class RootlyApi {
       name: entity.metadata.name,
     });
     const ownerGroupIds = await this.resolveOwnerGroupIds(entity);
+    const passthroughAttrs = extractPassthroughAttributes(entity.metadata.annotations, ROOTLY_ANNOTATION_SERVICE_ATTR_PREFIX);
+    const properties = extractProperties(entity.metadata.annotations, ROOTLY_ANNOTATION_SERVICE_PROPERTY_PREFIX);
     const init = {
       method: 'POST',
       headers: { 'Content-Type': 'application/vnd.api+json' },
@@ -490,6 +542,8 @@ export class RootlyApi {
         data: {
           type: 'services',
           attributes: {
+            ...passthroughAttrs,
+            ...(properties.length > 0 ? { properties } : {}),
             name:
               entity.metadata.annotations?.[ROOTLY_ANNOTATION_SERVICE_NAME] ||
               entity.metadata.name,
@@ -536,6 +590,8 @@ export class RootlyApi {
     }
 
     const ownerGroupIds = await this.resolveOwnerGroupIds(entity);
+    const passthroughAttrs = extractPassthroughAttributes(entity.metadata.annotations, ROOTLY_ANNOTATION_SERVICE_ATTR_PREFIX);
+    const properties = extractProperties(entity.metadata.annotations, ROOTLY_ANNOTATION_SERVICE_PROPERTY_PREFIX);
     const init2 = {
       method: 'PUT',
       headers: { 'Content-Type': 'application/vnd.api+json' },
@@ -543,6 +599,8 @@ export class RootlyApi {
         data: {
           type: 'services',
           attributes: {
+            ...passthroughAttrs,
+            ...(properties.length > 0 ? { properties } : {}),
             name:
               entity.metadata.annotations?.[ROOTLY_ANNOTATION_SERVICE_NAME] ||
               entity.metadata.name,
@@ -588,6 +646,7 @@ export class RootlyApi {
       kind: entity.kind,
       name: entity.metadata.name,
     });
+    const passthroughAttrs = extractPassthroughAttributes(entity.metadata.annotations, ROOTLY_ANNOTATION_FUNCTIONALITY_ATTR_PREFIX);
     const init = {
       method: 'POST',
       headers: { 'Content-Type': 'application/vnd.api+json' },
@@ -595,6 +654,7 @@ export class RootlyApi {
         data: {
           type: 'functionalities',
           attributes: {
+            ...passthroughAttrs,
             name:
               entity.metadata.annotations?.[
                 ROOTLY_ANNOTATION_FUNCTIONALITY_NAME
@@ -643,6 +703,7 @@ export class RootlyApi {
       await this.call(`/v1/functionalities/${old_functionality.id}`, init1);
     }
 
+    const passthroughAttrs = extractPassthroughAttributes(entity.metadata.annotations, ROOTLY_ANNOTATION_FUNCTIONALITY_ATTR_PREFIX);
     const init2 = {
       method: 'PUT',
       headers: { 'Content-Type': 'application/vnd.api+json' },
@@ -650,6 +711,7 @@ export class RootlyApi {
         data: {
           type: 'functionalities',
           attributes: {
+            ...passthroughAttrs,
             name:
               entity.metadata.annotations?.[
                 ROOTLY_ANNOTATION_FUNCTIONALITY_NAME
@@ -695,6 +757,7 @@ export class RootlyApi {
       kind: entity.kind,
       name: entity.metadata.name,
     });
+    const passthroughAttrs = extractPassthroughAttributes(entity.metadata.annotations, ROOTLY_ANNOTATION_TEAM_ATTR_PREFIX);
     const init = {
       method: 'POST',
       headers: { 'Content-Type': 'application/vnd.api+json' },
@@ -702,6 +765,7 @@ export class RootlyApi {
         data: {
           type: 'teams',
           attributes: {
+            ...passthroughAttrs,
             name:
               entity.metadata.annotations?.[ROOTLY_ANNOTATION_TEAM_NAME] ||
               entity.metadata.name,
@@ -746,6 +810,7 @@ export class RootlyApi {
       await this.call(`/v1/teams/${old_team.id}`, init1);
     }
 
+    const passthroughAttrs = extractPassthroughAttributes(entity.metadata.annotations, ROOTLY_ANNOTATION_TEAM_ATTR_PREFIX);
     const init2 = {
       method: 'PUT',
       headers: { 'Content-Type': 'application/vnd.api+json' },
@@ -753,6 +818,7 @@ export class RootlyApi {
         data: {
           type: 'teams',
           attributes: {
+            ...passthroughAttrs,
             name:
               entity.metadata.annotations?.[ROOTLY_ANNOTATION_TEAM_NAME] ||
               entity.metadata.name,
@@ -885,6 +951,8 @@ export class RootlyApi {
       kind: entity.kind,
       name: entity.metadata.name,
     });
+    const passthroughAttrs = extractPassthroughAttributes(entity.metadata.annotations, ROOTLY_ANNOTATION_CATALOG_ENTITY_ATTR_PREFIX);
+    const properties = extractProperties(entity.metadata.annotations, ROOTLY_ANNOTATION_CATALOG_ENTITY_PROPERTY_PREFIX);
     const init = {
       method: 'POST',
       headers: { 'Content-Type': 'application/vnd.api+json' },
@@ -892,6 +960,8 @@ export class RootlyApi {
         data: {
           type: 'catalog_entities',
           attributes: {
+            ...passthroughAttrs,
+            ...(properties.length > 0 ? { properties } : {}),
             name:
               entity.metadata.annotations?.[ROOTLY_ANNOTATION_CATALOG_ENTITY_NAME] ||
               entity.metadata.name,
@@ -937,6 +1007,8 @@ export class RootlyApi {
       await this.call(`/v1/catalog_entities/${old_catalogEntity.id}`, init1);
     }
 
+    const passthroughAttrs = extractPassthroughAttributes(entity.metadata.annotations, ROOTLY_ANNOTATION_CATALOG_ENTITY_ATTR_PREFIX);
+    const properties = extractProperties(entity.metadata.annotations, ROOTLY_ANNOTATION_CATALOG_ENTITY_PROPERTY_PREFIX);
     const init2 = {
       method: 'PUT',
       headers: { 'Content-Type': 'application/vnd.api+json' },
@@ -944,6 +1016,8 @@ export class RootlyApi {
         data: {
           type: 'catalog_entities',
           attributes: {
+            ...passthroughAttrs,
+            ...(properties.length > 0 ? { properties } : {}),
             name:
               entity.metadata.annotations?.[ROOTLY_ANNOTATION_CATALOG_ENTITY_NAME] ||
               entity.metadata.name,
diff --git a/src/constants.ts b/src/constants.ts
index e3aefe9..45cf6e3 100644
--- a/src/constants.ts
+++ b/src/constants.ts
@@ -38,3 +38,15 @@ export const ROOTLY_ANNOTATION_CATALOG_ID = "rootly.com/catalog-id";
 export const ROOTLY_ANNOTATION_CATALOG_SLUG = "rootly.com/catalog-slug";
 /** @public */
 export const ROOTLY_ANNOTATION_CATALOG_DESCRIPTION = "rootly.com/catalog-description";
+/** @public */
+export const ROOTLY_ANNOTATION_SERVICE_ATTR_PREFIX = "rootly.com/service-attr-";
+/** @public */
+export const ROOTLY_ANNOTATION_SERVICE_PROPERTY_PREFIX = "rootly.com/service-property-";
+/** @public */
+export const ROOTLY_ANNOTATION_FUNCTIONALITY_ATTR_PREFIX = "rootly.com/functionality-attr-";
+/** @public */
+export const ROOTLY_ANNOTATION_TEAM_ATTR_PREFIX = "rootly.com/team-attr-";
+/** @public */
+export const ROOTLY_ANNOTATION_CATALOG_ENTITY_ATTR_PREFIX = "rootly.com/catalog-entity-attr-";
+/** @public */
+export const ROOTLY_ANNOTATION_CATALOG_ENTITY_PROPERTY_PREFIX = "rootly.com/catalog-entity-property-";