Google HomeGraph API

Name: HomeGraph API
Brand: HomeGraph API
Availability: InStock

✓ Official Vendor SpecIOTHome Automationoauth25 EndpointsREST

Install Jentic One Beta

Connect the HomeGraph API to your agent

Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the HomeGraph API, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.

Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.

Step 1: Jentic One Host machine

# On the machine that will host your Jentic One instance:
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh

Step 2: Agent machine

# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh
jentic register       # connects your agent to your Jentic One instance

Jentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.

Capabilities

What an agent can do with HomeGraph API.

Push real-time state and notification updates from device cloud to Google Assistant via reportStateAndNotification

Trigger a fresh device list sync for a user after the integration adds or removes hardware

Query the current cached state of a user's devices known to Google Assistant

GET STARTED

Start building with HomeGraph API

Explore with Jentic

View OpenAPI Document

For Agents

Keep Google Assistant in sync with cloud-to-cloud smart-home devices by pushing state changes and triggering device syncs after add/remove events.

Use for: Tell Google Assistant a smart light just turned on, Trigger a request sync after a user adds a new thermostat, Check the current state of a user's smart-home devices, Send a notification that a doorbell was pressed

Not supported: Does not fulfil voice intents, control devices directly, or stream telemetry - use for syncing cloud-to-cloud smart-home device state with Google Assistant only.

The HomeGraph API is the cloud surface that smart-home device makers use to keep Google Assistant in sync with the state of devices in a user's home. Cloud-to-cloud integrations call HomeGraph to request a fresh device sync after the user adds or removes hardware, push state and notification updates when a device changes (lights turn on, door is unlocked), and query the current state of devices Assistant has cached. The API is paired with the Smart Home action fulfilment pattern: device makers serve their own intent handlers and use HomeGraph to keep Google's home graph in sync.

Use Cases

Patterns agents use HomeGraph API for, with concrete tasks.

★ Cloud-to-Cloud Smart Home State Sync

A smart-home device manufacturer with a cloud backend uses HomeGraph's reportStateAndNotification endpoint to push every device-state change (light brightness, lock state, thermostat setpoint) into Google's home graph in near real time. This keeps Assistant responses ("Hey Google, is the front door locked?") accurate without Assistant having to query the device cloud on demand. The agentUserId in the payload identifies which user's home graph to update.

For agentUserId user-123, call POST /v1/devices:reportStateAndNotification with a payload that sets device-456's on state to true and brightness to 80, and report the requestId returned.

Device Onboarding Refresh

When a user adds or removes a device in the manufacturer's app, the integration calls POST /v1/devices:requestSync with the user's agentUserId. Google then re-invokes the integration's SYNC intent handler and refreshes the home graph. This avoids the user having to say "Hey Google, sync my devices."

After a user adds a new smart plug, call POST /v1/devices:requestSync with the user's agentUserId and confirm the response is a 200 with an empty body.

Account Unlink Cleanup

When a user unlinks the manufacturer's Google account or deletes their cloud account, the integration calls DELETE /v1/{+agentUserId} on HomeGraph to remove their devices from the home graph. This keeps Assistant from offering devices the user no longer has and is required for full Works With Google Home certification.

For agentUserId user-789 who has just unlinked their account, call DELETE /v1/{+agentUserId} and verify the response is 200.

AI Agent Diagnostic for Smart Home Integrations

An AI agent helping a smart-home developer debug their cloud-to-cloud integration uses Jentic to call HomeGraph's devices.query and devices.sync endpoints with the developer's service account. The agent compares the device payload Google sees with what the manufacturer's cloud thinks it sent and surfaces mismatches. Jentic isolates the service-account credential so the agent never holds raw OAuth secrets.

For agentUserId user-test, call POST /v1/devices:query for device-abc and POST /v1/devices:sync, then diff the two payloads and list devices present in one but not the other.

Key Endpoints

5 endpoints — the homegraph api is the cloud surface that smart-home device makers use to keep google assistant in sync with the state of devices in a user's home.

METHOD

PATH

DESCRIPTION

POST

/v1/devices:reportStateAndNotification

Push real-time device state and notifications to Google Assistant

POST

/v1/devices:requestSync

Trigger Google to re-fetch the device list for an agent user

POST

/v1/devices:query

Query Google's cached state for the user's devices

POST

/v1/devices:sync

Server-side validate the SYNC intent payload for an agent user

DELETE

/v1/{+agentUserId}

Unlink a user and remove their devices from the home graph

POST

/v1/devices:reportStateAndNotification

Push real-time device state and notifications to Google Assistant

POST

/v1/devices:requestSync

Trigger Google to re-fetch the device list for an agent user

POST

/v1/devices:query

Query Google's cached state for the user's devices

POST

/v1/devices:sync

Server-side validate the SYNC intent payload for an agent user

DELETE

/v1/{+agentUserId}

Unlink a user and remove their devices from the home graph

Why Jentic?

Three things that make agents converge on Jentic-routed access.

Credential isolation

Your smart-home service-account credential is stored once, encrypted, by your own Jentic One instance and injected at execution time as a short-lived access token. The service-account JSON never enters the agent's prompt, logs, or context.

Intent-based discovery

Agents search Jentic by intent such as 'report smart home device state' or 'request a device sync', and Jentic returns the matching operation with its full state schema so the agent builds the payload without browsing the smart-home docs.

Time to first call

FAQs

Specific to using HomeGraph API through Jentic.

What authentication does the HomeGraph API use?

Google OAuth 2.0 via a service account associated with the project's smart home action. The service-account JSON key is exchanged for an access token. Through Jentic the JSON key is held in the vault and a scoped access token is minted at call time.

Can I push device state changes in real time?

Yes. POST /v1/devices:reportStateAndNotification accepts batched state updates for an agentUserId and is designed to be called whenever a device changes state in the manufacturer's cloud. Google updates the home graph and emits any user-facing notifications.

What are the rate limits for the HomeGraph API?

Google enforces a per-project quota; reportStateAndNotification is the highest-traffic endpoint and supports thousands of QPS in production. Exact limits are visible in Cloud Console quotas for the HomeGraph API.

How do I trigger a device list refresh through Jentic?

Search Jentic with 'request sync homegraph', load the POST /v1/devices:requestSync operation, and execute with the user's agentUserId in the request body. Jentic handles OAuth and returns the empty 200 response.

Does HomeGraph fulfil voice commands directly?

No. Voice commands are handled by your Smart Home action's intent fulfilment (EXECUTE, QUERY, SYNC). HomeGraph is the side channel for keeping Google's cached device state in sync between those intents.

Can I limit what my agent is allowed to do with the HomeGraph API?

Yes. Because you run Jentic One yourself, your own rules decide which HomeGraph operations the agent may call, and the API targets devices through the request body rather than the URL path, so you scope by operation. You choose the allowed set, so granting only reportStateAndNotification lets the agent push device state and notifications while it can never trigger requestSync, query cached state, or delete an agent user's mapping. Your smart-home service-account credential is held by your own instance and injected at call time, so the agent acts only within the operations you permit.

Google HomeGraph API

Connect the HomeGraph API to your agent

Capabilities

Start building with HomeGraph API

Use Cases

Key Endpoints

Why Jentic?

Related APIs

FAQs