Improve vendor facing doc to collect consent related information.

extensions/amp-consent/amp-consent.md

@@ -33,7 +33,7 @@ As a publisher, you can use the `<amp-consent>` component to implement user cont
 - Capture the user’s consent decision.
 - Makes the user’s setting available to elements on the AMP page to modify the page’s behavior.
 
-If you are a vendor that wants to customize your component's behavior based on amp-consent, you can read more [here](https://github.com/ampproject/amphtml/blob/master/extensions/amp-consent/customizing-extension-behaviors-on-consent.md).
+If you are a vendor that wants to customize your component's behavior based on amp-consent, or need to collect more advanced consent information you can read more [here](https://github.com/ampproject/amphtml/blob/master/extensions/amp-consent/customizing-extension-behaviors-on-consent.md).
 
 ## Usage
 

extensions/amp-consent/customizing-extension-behaviors-on-consent.md

@@ -28,16 +28,41 @@ getConsentPolicy() {
 
 ## Advanced blocking behaviors
 
-If the vendor wants to customize an AMP extension behaviors based on user control, use the `getConsentPolicyState` API.
+### On Consent State
 
-`getConsentPolicyState` returns a promise with one of the following values:
+AMP provides the consent state information for vendors to customize their behavior based on user control.
+
+The state has the following valid values.
 
 - `null` : no `<amp-consent>` is included
 - `CONSENT_POLICY_STATE.UNKNOWN` : The consent state is unknown
 - `CONSENT_POLICY_STATE.SUFFICIENT` : The consent is accepted
 - `CONSENT_POLICY_STATE.INSUFFICIENT` : The consent is rejected
 - `CONSENT_POLICY_STATE.UNKNOWN_NOT_REQUIRED` : The consent state is unknown, and `<amp-consent>` is informed to not prompt UI.
 
-In addition to the consent state, the vendor can also use the
+#### If you integrate with AMP as a first party AMP extension
+Use the `getConsentPolicyState` API. It returns a promise with one of the `CONSENT_POLICY_STATE` value.
+
+#### If you integrate with AMP as a third party ad vendor
+Access the value within the ad iframe using `window.context.initialConsentState`. Check [this](https://github.com/ampproject/amphtml/blob/master/ads/README.md#amp-consent-integration) for more details.
+
+#### If you integrate with AMP as an analytics vendor
+Get the value using `CONSENT_STATE` macro, or `${consentState}`. A request with the varaible will only be sent out after the state has resolved to one of the above state.
+
+### On Consent String ###
+
+AMP collects raw consent string value from `checkConsentHref` endpoint or from the CMP. The it passes the raw consent string to vendors without modification.
+It is then up to the vendor to intepret the string and customize behavior accordingly. AMP recommends handle the string on the server side.
+
+AMP will always pass the local stored consent string if there's one. Update to the string will only be reflected the next page load.
+
+#### If you integrate with AMP as a first party AMP extension
+Use the `getConsentPolicyInfo` API. `getConsentPolicyInfo` returns a promise with the raw consent string value.
+
+Ways to get the consent string for ad/analytics vendors coming soon.
+
+### On Related Information
+
+In addition to the consent state and consent string, AMP extensions can also use the
 `getConsentPolicySharedData` API to receive additional consent related information about
 the user from the page owner. See [this](https://github.com/ampproject/amphtml/blob/master/extensions/amp-consent/amp-consent.md#response) for details about the `shareData`.