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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteChoose Marrow if you want an MCP server on your iPhone and your AI client can reach it over the local network; choose MetricBridge if you prefer a local server that reads Apple Health data exported to JSON files. The key difference is how data reaches the agent: a network endpoint on the phone (or an optional Marrow mirror) versus files available to a computer running MetricBridge’s server. The comparison below is based on vendor product pages and project documentation, not independent performance or security testing.
How the two Apple Health MCP options work
Both options are described as ways to make Apple Health data available to AI tools, but they use different paths. With Marrow, the iPhone serves the data. With MetricBridge, its companion app exports data to JSON files, and a server on a computer reads those files and exposes tools over standard input and output (stdio).
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| Question | Marrow | MetricBridge |
|---|---|---|
| Where does MCP run? | On the iPhone over the local network; an optional self-hosted mirror is also documented. Marrow product page and Marrow setup documentation | A local server reads exported JSON files and communicates with the client over stdio. health-export-mcp project |
| What must the agent or client be able to access? | The phone’s network endpoint, or the mirror endpoint if you set one up. Marrow setup documentation and Marrow mirror documentation | The computer running the server and the exported files it reads. health-export-mcp project |
| Is additional hardware necessarily required? | No additional server is required for the on-phone option. The vendor says a mirror can run on an existing Pi, NAS, or old laptop. Marrow setup documentation and Marrow mirror documentation | The project describes a local server, but the project documentation does not establish that new hardware is needed. health-export-mcp project |
| What should you check first? | Whether your client can reach the iPhone on the network you plan to use, and whether you need a mirror when the phone is away. Marrow setup documentation and Marrow mirror documentation | Whether the export destination is accessible to the server and how often the app refreshes the files. Check the current app documentation for those details. health-export-mcp project |
Marrow: MCP served from the iPhone
What the on-phone setup provides
Marrow describes its iOS app as free, with Apple Health access and an MCP setup flow. Its setup documentation says the user enables the on-phone server, which is read-only, uses bearer-token authentication, and binds to the local network. The stated requirements are Apple Health and iOS 17 or later. Marrow says this option does not require a Marrow account or use a hosted API. See the Marrow product page and Marrow setup documentation.
Marrow lists coverage of 178 data series on its product page, retrieved on October 7, 2026. That is the vendor’s coverage count; it does not establish data quality, accuracy, or which series will matter for a particular agent workflow. Marrow product page
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When the phone is not available
Marrow also documents an optional self-hosted mirror for access when the phone is away. The mirror can run on a Pi, NAS, or old laptop. Marrow recommends using a LAN or tailnet and warns against forwarding the server’s port to the open internet. The mirror adds a host to manage, so it is most relevant when reaching the phone directly is not practical. Marrow mirror documentation
MetricBridge: a local server backed by exported files
What “zero-dependency” describes
The health-export-mcp project describes its server as read-only and having no external package dependencies. The MetricBridge companion app exports Apple Health data into JSON files in a location chosen by the user; the server reads those files and exposes its tools over stdio. “Zero-dependency” refers to the project’s external package dependencies, not to the absence of setup: the app, exported files, local server, and an MCP client still have to fit together. health-export-mcp project
The project states coverage of 190 Apple Health metrics, in documentation retrieved on October 7, 2026. As with Marrow’s count, this is a vendor/project-stated coverage figure, not an independent measure of accuracy or usefulness. health-export-mcp project
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Check file access and freshness
Because the server reads exported files, confirm that the chosen destination is available to the computer running it. Also check how frequently the companion app refreshes the export; the project materials cited here do not establish a refresh interval. If a client sees older values than expected, file accessibility and export freshness are natural first checks. health-export-mcp project
Choose by where your MCP client can reach the data
- Choose Marrow’s on-phone path if you want to avoid maintaining a separate server and your client can connect to the iPhone over the local network.
- Consider Marrow’s mirror if the phone may be away or unreachable, and you are comfortable hosting and maintaining a service on a Pi, NAS, or old laptop.
- Choose MetricBridge’s file-based path if you want the server to read local JSON exports and your client can use a stdio server on the computer where those files are accessible.
- Verify the data timing you need. Marrow’s direct path depends on reaching the phone; MetricBridge depends on the exported files being current. Check each product’s current setup guidance rather than assuming either is continuously refreshed.
In practice, “local-first” does not by itself tell you whether an agent can get the data. The deciding detail is whether your MCP client can reach a phone endpoint, a mirror endpoint, or the computer and files used by MetricBridge.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Pricing and availability to verify
Marrow describes its core app and MCP access as free, with an optional Pro offering. MetricBridge’s App Store listing describes an initial seven-day free trial followed by a one-time purchase that unlocks export, on-device Ask, and Weekly Brief. That trial and purchase description was retrieved on October 7, 2026; prices and terms can vary by storefront and change, so consult the live App Store listing before deciding. Marrow product page and MetricBridge App Store listing
Security and evidence boundaries
Marrow documents its phone server as user-enabled, read-only, bearer-token authenticated, and bound to the local network. For its mirror, the vendor recommends a LAN or tailnet and cautions against exposing the service through open-internet port forwarding. MetricBridge describes its server as read-only and local. These are product and project descriptions; they do not establish that either option has undergone an independent security audit. Follow the current setup guidance for the configuration you use.
The available documentation also does not establish a comparative performance benchmark or clinical suitability. These integrations can make health data available to AI tools, but their presence is not medical advice and should not be treated as a clinical assessment.
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