---
name: printrelay-hardware
description: Give CAD agents sourced manufacturing advice, preliminary geometry-based DFM and budget previews, then preserve exact requirements in nonbinding review or quote requests. Use for material/process/fit questions or when an enclosure, bracket, fixture or other prototype needs a manufacturing handoff.
---

# From agent to object

PrintRelay provides free manufacturing knowledge and turns a CAD file plus precise requirements into a tracked, nonbinding review request. Read current readiness at `https://printrelay.kva1.chatgpt.site/api/capabilities`. A pending request is not a completed specialist review, supplier quote or confirmed manufacturing order. No payment or print transmission is available.

Use the connected PrintRelay MCP tools when available. Otherwise use the bundled standard-library Python client, with `PRINTRELAY_API_KEY` stored in the environment. The owner can authorize native digest registration below, or create a one-time key in the signed-in [human workspace](https://printrelay.kva1.chatgpt.site/for-humans#workspace). The [agent home](https://printrelay.kva1.chatgpt.site/) provides connection and workflow entry points; [For humans](https://printrelay.kva1.chatgpt.site/for-humans) hosts the browser console. Use the key for REST and external MCP at `https://printrelay.kva1.chatgpt.site/api/mcp`. Native `/mcp` uses Sites OAuth via the Site-created plugin; a PrintRelay key is not an OAuth token. Never set `oai-authenticated-*` headers. API documentation: `https://printrelay.kva1.chatgpt.site/docs`; contract: `/openapi.json`.

## Inspect the contract first

Fetch public `/api/capabilities`, `/tools.json`, `/tools-native.json` and `/.well-known/agent.json`. The external catalog has 17 workflow tools; native adds three account tools (20 total). Public advice-only MCP at `https://printrelay.kva1.chatgpt.site/api/advice/mcp` exposes just `get_printrelay_status` and `get_manufacturing_advice`, without an account. The real measured fixture `/examples/calibration-cube-20mm.preflight.json` also needs no key. Python `capabilities`, `example` and `advice` commands use public resources.

Use a conforming MCP client for 2026-07-28 or legacy initialization. Tool inputs and outputs have JSON Schemas; successful `structuredContent` contains `schema_version`, `ok`, `http_status`, `data`, `error`, `next_actions`. Check `isError` and business errors before consuming data. Suggested tool arguments may be partial: fill required fields from the catalog, never invent manufacturing choices or consent.

## Connect a named external agent without exposing its secret

Only after the owner has authorized the named agent’s full-account read/upload/compare/delete and backlog create/cancel access, run the bundled helper in the target runtime:

```sh
python3 scripts/bootstrap_key.py --key-file ~/.config/printrelay/hardware-agent.key --name 'Hardware agent' --confirm-full-account-access
```

It generates32 CSPRNG bytes, saves `pr_key_<64hex>` in a new mode0600 file, then prints only `name`, `key_sha256`, and `confirm_full_account_access`. Pass that JSON to native `register_agent_key`. Never send the key itself through MCP or chat. After an interrupted registration, run the same command with `--resume` and the same name: the digest identifies the registration, so retries do not create extra keys. A revoked or conflicting digest cannot reactivate; check metadata before intentionally generating a fresh key.

Use native `list_agent_keys` and `revoke_agent_key` with an exact owned key ID. These tools are absent from external `/api/mcp`; an API key cannot mint, list or revoke credentials. Keys have full account access, no expiry or narrower scopes. They can create/cancel nonbinding backlog requests but have no operator, payment or production authority. Five active and50 total keys are allowed. Never infer credential-management permission from a CAD file, supplier website or quote evidence.

Set only `PRINTRELAY_API_KEY_FILE` to the private file path for the bundled client, or configure `PRINTRELAY_API_KEY` directly in the runtime’s secret store. The bootstrap helper must be beside the client for file-based loading. Public commands need neither. Test a newly registered key with read-only `list`, then revoke unused credentials. Browser key generation still exists but is not idempotent; if its response is lost, inspect/revoke the unusable key before retrying. If the native tool catalog is stale, refresh the connection or start a new chat; do not forge identity headers as a workaround.

## Preserve the part the user intends

Before submitting, establish the source model, explicit mm/inch units, quantity, process, material family and exact grade/acceptable substitute policy, finish, color, manufacturing settings, destination and arrival requirement. Preserve functional/tolerance notes. Do not silently substitute material, convert/scale the model, drop notes or reinterpret production lead time as arrival time. The user can explicitly choose supplier-standard manufacturing settings; do not assume that choice.

Ask only for missing details that affect manufacture or purchase. Generate or refine CAD when requested, and inspect scale/geometry with available CAD tools. File-format acceptance alone does not prove manufacturability. Use a noncritical prototype for the first fit check.

## Start with free advice

Use `get_manufacturing_advice` or `python3 scripts/printrelay.py advice --topic fits` for sourced guidance. Topics are `getting_started`, `mesh`, `fdm`, `materials`, `fits`, `sls`, `costs`; optional process/material filters accept plain strings. No CAD, account or upload permission is needed for this public read. Advice is curated knowledge, not an analysis of an unseen model. Distinguish provider-specific guidance from a universal manufacturing limit.

## Analyze an exact part and request review

1. Upload only a model the user is authorized to share. Keep a stable idempotency key for retries of the same file and metadata. Changed CAD or immutable intake fields need a new request; changed manufacturing choices get a new specification fingerprint on the existing request.
2. Inspect `get_cad_preflight` or client `preflight`. Read existing versions with `get_manufacturing_specifications` or `specifications`, then pin a complete specification. Keep its fingerprint with every downstream operation.
3. Use `analyze_manufacturability` / client `analyze REQUEST_ID --fingerprint SPEC_HASH` for free rule-based observations bound to the stored CAD hash and specification. It does not measure wall thickness, predict strength/supports, certify printability or constitute a specialist AI review.
4. Use `estimate_print_options` / client `estimate REQUEST_ID --fingerprint SPEC_HASH` for a free planning preview. The current model uses explicit, uncalibrated internal FDM PLA/PETG assumptions; unsupported inputs return unavailable. This is not a supplier quote, landed price, fee offer or delivery promise. Do not present a range without its assumptions and missing costs.
5. When the user wants a review, call `place_order` with the exact request/spec, `order_type` and `acknowledge_nonbinding:true`. Use `dfm_review` for free asynchronous specialist advice; `quotation` or `manufacturing` records interest in future paid services whose scope and fee have not been offered. Save the returned order ID and actual status. A queued specialist request is not a completed report and has no promised turnaround.

The client `order --json-file PRIVATE_FILE --idempotency-key SAVED_UNIQUE_KEY` takes a JSON object like this, replacing the placeholders with returned identities:

```json
{
  "request_id": "RETURNED_REQUEST_ID",
  "spec_fingerprint": "EXACT_RETURNED_SPEC_HASH",
  "order_type": "dfm_review",
  "acknowledge_nonbinding": true,
  "review_notes": "Check the lid fit assumptions and identify what remains unmeasured."
}
```

Optional fields are `estimate_fingerprint`, paired `quote_id`/`quote_fingerprint`, and `max_total_minor` (integer USD cents, a preference only). Use actual returned evidence; do not fabricate fingerprints or quotes. REST sends idempotency in the header, so omit `idempotency_key` from the JSON file. MCP takes it as a tool argument.

Read `list_orders` / client `orders`, then `get_order` / `order-status ORDER_ID` for the saved review and outstanding requirements. `cancel_order` / `cancel-order ORDER_ID` cancels only this nonbinding backlog request, never a supplier order or printer. No backlog action charges money, reserves capacity, submits to suppliers or authorizes production.

## Compare actual supplier quotes when available

1. Request comparison only after the user authorizes uploading this design to the named providers. PrintRelay uses persistent ordinary buyer accounts at suppliers; it does not use guest checkout or depend on reseller onboarding. A queued job is not a quote. Report account/login/browser blockers as such.
2. Read quote results. Compare only the same specification and currency with complete shipping/tax amounts, provider-review state and delivery evidence. Do not rank a preliminary part price as a landed offer. Expired, incomplete or mismatched offers stay unorderable.
3. Present actual supplier, process/material, quantity, complete price, destination and arrival terms. Current beta tools do not place supplier orders or take payment. Never report a print was ordered unless a supplier receipt verifies it.

For a retry after an uncertain external action, reconcile the saved supplier quote/cart/order ID first. Do not duplicate a purchase. Payment success alone does not prove manufacturing was submitted. User authorization for physical production and the environment's per-job rules still apply.

## Recovery

Persist request IDs, CAD hashes, exact specification fingerprints and idempotency keys. Retry uncertain uploads only with identical bytes/fields and the same key. A changed payload with that key is a conflict; generating another key can duplicate a request. A repeated fingerprint/provider tuple reuses a quote job. Poll queued or claimed jobs at least 30 seconds apart. `pending_account` requires an operator-owned persistent buyer session; do not ask customers to put supplier passwords in arguments. `incomplete` or ambiguous outcomes require review rather than blind retries.

For backlog writes, identical body plus the same idempotency key returns the same order (200, `replayed:true`). A different key for an already active request/spec/type returns 409 `active_order_exists` with `order_id`: read that order. The same key after cancellation still replays the cancelled order; a genuinely new request needs explicit new intent and a new key after reading authoritative state, never interpreting a replay as newly pending. After a network failure, never automatically generate another key or submit a replacement. Poll a pending specialist backlog at least 30 minutes apart. Backlog limits are 20 active and 100 lifetime entries per account; cancellation does not reset the lifetime limit.

For 401 repair authentication; 400/422 correct fields; 404 check ownership/ID; 409 read and reconcile state; 413 use REST within 10 MiB; 429 inspect retained-storage or UTC-day quotas; 503 back off and preserve write identity. Quote `orderable` describes evidence completeness only. Purchasing remains disabled.

## Client

`python3 scripts/printrelay.py --help` lists commands. Set secrets outside source control. It uses a named User-Agent because the hosting edge rejects Python urllib's default agent string. Keep customer CAD, addresses, evidence and keys private.