# Tethered Trust

> Compatibility intelligence for AI agents: check that a part, accessory or appliance fits *before* buying it. Answers come from a curated compatibility graph and deterministic rules, with evidence and a confidence score. AI is only used to read specs of products the graph doesn't know yet, and those readings are held for human review.

Website: https://tetheredtrust.com  ·  Operator: Chimes In LLC  ·  Contact: support@chimes-in.com

## Connect
- MCP (Streamable HTTP, stateless, no auth needed during the launch): https://tetheredtrust.com/mcp
- Claude: Settings › Connectors › Add custom connector › paste the URL above
- Claude Code: `claude mcp add --transport http tethered-trust https://tetheredtrust.com/mcp`
- Cursor (~/.cursor/mcp.json): `{"mcpServers": {"tethered-trust": {"url": "https://tetheredtrust.com/mcp"}}}`
- ChatGPT (developer mode): add a custom connector and paste the URL above
- HTTP API: https://tetheredtrust.com/v1 (JSON description of every operation)
- Free during the launch, no key needed. An API key (`Authorization: Bearer tt_...`) raises rate limits.
- Paid access (when switched on): `POST https://tetheredtrust.com/v1/paid/check|fit|parts`, paid with x402 v2 (`PAYMENT-SIGNATURE` header, or `_meta["x402/payment"]` over MCP) or with prepaid credits on an API key (https://tetheredtrust.com/credits). Charged only for completed answers, never for errors or needs_detail, and never dependent on the verdict.

## Coverage
- **Computers & consoles** (`computers`): RAM, M.2 SSDs and USB-C chargers for laptops, handhelds, mini PCs and consoles. Browse: https://tetheredtrust.com/coverage/computers
- **Phones, tablets & watches** (`mobile`): Wired and wireless chargers (USB-C PD, MagSafe, Qi2) and watch bands. Browse: https://tetheredtrust.com/coverage/mobile
- **Cameras** (`cameras`): Lens mounts and adapters, batteries and memory cards. Browse: https://tetheredtrust.com/coverage/cameras
- **Cordless power tools** (`power-tools`): Battery platforms, batteries, chargers and bare tools across brands. Browse: https://tetheredtrust.com/coverage/power-tools
- **Printers** (`printers`): Ink, toner and drum units, including region locks and HP+ rules. Browse: https://tetheredtrust.com/coverage/printers
- **Appliances** (`appliances`): Refrigerator water and air filters, plus installation fit. Browse: https://tetheredtrust.com/coverage/appliances
- **Smart home & lighting** (`smart-home`): Matter, Thread, Zigbee, HomeKit, Alexa and Google Home hubs and accessories, plus bulb bases. Browse: https://tetheredtrust.com/coverage/smart-home

## Operations

### GET /v1/how-it-works  (MCP tool: `how_it_works`)
What Tethered Trust is, what it covers, pricing and terms, and how an assistant should use it before a purchase. Call once if unsure; you don't need it for every check.
Price: free

### GET /v1/coverage?category=  (MCP tool: `list_coverage`)
Which product categories and models are in the compatibility graph, with counts. Pass a category to list its models. Covers computers & consoles (RAM, M.2 SSDs, USB-C chargers), phones/tablets/watches (USB-C PD, MagSafe, Qi2, watch bands), cameras (lens mounts, adapters, batteries, memory cards), cordless power tools (battery platforms, batteries, chargers), printers (ink, toner, drums), appliances (refrigerator filters, installation fit) and smart home (Matter, Thread, Zigbee, HomeKit, Alexa, Google Home, bulb bases).
Price: free

### GET /v1/resolve?query=  (MCP tool: `resolve_product`)
Look up one product in the Tethered Trust graph by name or model number and get its structured specs, what it accepts (mounts, battery platforms, cartridges, protocols) and what it fits.
Price: free

### POST /v1/check  (MCP tool: `check_compatibility`)
Will this exact part or accessory work with that exact device? Use before recommending or buying. Covers computers & consoles (RAM, M.2 SSDs, USB-C chargers), phones/tablets/watches (USB-C PD, MagSafe, Qi2, watch bands), cameras (lens mounts, adapters, batteries, memory cards), cordless power tools (battery platforms, batteries, chargers), printers (ink, toner, drums), appliances (refrigerator filters, installation fit) and smart home (Matter, Thread, Zigbee, HomeKit, Alexa, Google Home, bulb bases). Returns a verdict (compatible / compatible_with_caveats / incompatible / uncertain / needs_detail) with confidence, the rules checked, caveats and evidence links.
Price: free during the launch on this endpoint; $0.05 per completed answer on /v1/paid/* (x402 or prepaid credits)

### POST /v1/parts  (MCP tool: `find_parts`)
Which parts and accessories fit this model? OEM parts first, then verified alternatives: e.g. a refrigerator's water filter, a printer's cartridges, a camera's lenses and batteries, a tool's batteries, or the RAM, SSDs and chargers that fit a computer.
Price: free during the launch on this endpoint; $0.05 per completed answer on /v1/paid/* (x402 or prepaid credits)

### POST /v1/fit  (MCP tool: `check_fit`)
Will this appliance physically fit this space? Compares dimensions plus typical installation clearances and required connections (power, water, gas).
Price: free during the launch on this endpoint; $0.05 per completed answer on /v1/paid/* (x402 or prepaid credits)

### POST /v1/receipts/verify  (MCP tool: `verify_receipt`)
Check a Tethered Trust receipt: is the signature ours, is it still within valid_until, and have the records behind it changed since? A valid receipt proves what we said and when; it doesn't guarantee the verdict was right.
Price: free

### POST /v1/outcome  (MCP tool: `report_outcome`)
After a purchase, report whether it actually fit. Free, safe to call, and only the first report per check counts. Reports are weighted by level: self_reported (website), agent_reported (anonymous API/MCP), partner_reported (API key holders) and order_confirmed (order evidence we've confirmed). Only the last two can raise future confidence.
Price: free

## Terms
Use is subject to the Terms of Service (https://tetheredtrust.com/terms) and the API & Agent Terms (https://tetheredtrust.com/api-terms). Answers are informational: present caveats and confidence honestly, and tell people to confirm with the manufacturer before buying or installing. Privacy: https://tetheredtrust.com/privacy. How answers are made: https://tetheredtrust.com/methodology.

## How to use it well
- Pass exact model numbers when you have them. "ThinkPad T480" beats "Lenovo laptop"; "HP OfficeJet Pro 9015e" beats "HP printer".
- Respect the verdict: `needs_detail` comes with a `missing` list of what to ask the person.
- `verified: false` means some specs came from the person's text, from AI, or from a source we haven't reviewed; say so.
- Read the caveats aloud to the person: region-locked cartridges, adapters, crop modes and firmware notes live there.
- Keep the `receipt` that comes with each answer. It's a signed record (EdDSA JWS) of exactly what we said and when; anyone can check it with `verify_receipt` or https://tetheredtrust.com/.well-known/tethered-trust-keys.json. It proves what we said, not that we were right.
- Re-check after `valid_until`.
- After the purchase, call `report_outcome`. It's free and improves future answers. With an API key your reports count as partner reports; include order details in `evidence` to have them confirmed.