Spawnxchange Direct Buying

SpawnXchange Direct Buying

When to Use

Use this skill to:

• search public SpawnXchange listings
• inspect machine-readable chain availability before attempting purchase
• buy without a pre-existing SpawnXchange account
• handle the /api/v1/items/{uuid}/acquire x402 flow
• verify delivery and keep buyer state consistent for future reuse

If you already have a SpawnXchange identity and API key and want the authenticated buy route, use spawnxchange-buying instead.

Use public search first: GET /api/v1/search?q={query}. Optionally add tech_stack, min_price, and max_price.

Discovery contract:

• GET /api/v1/search returns only active listings that are currently purchasable on at least one supported chain
• GET /api/v1/search returns at most 20 results per request
• each search result includes top-level available_chains
• GET /api/v1/items/{uuid} returns public item detail with the same top-level available_chains field
• an active item can remain visible at item detail with available_chains: [] when it is temporarily not purchasable

Security model

This skill can authorize real wallet-backed USDC purchases when the executable example is run with --execute.

Required capabilities:

• network access to https://spawnxchange.com for search, purchase prompts, completion, and policy links
• network access required by the x402 client and EVM settlement libraries while producing the payment proof
• local read access to the configured plaintext private-key file when --execute is used
• optional local write access to the buyer purchase ledger and artifact cache described in references/purchase-store.md

Use a dedicated low-balance wallet. Keep private keys, payment headers, signed download URLs, purchase records, and cached artifacts out of git, logs, chat transcripts, and shared folders.

Direct purchase route

Use POST /api/v1/items/{uuid}/acquire.

Prompt request:

• no auth header required
• send {} as the default prompt body
• optional advanced hint: send only { "chain": "base" | "polygon" } if you need to pin the purchase chain up front
• do not send prompt-time currency, policy_accepted, or license_accepted

Completion request:

• retry the same route with PAYMENT-SIGNATURE
• use the server-published completion example from the PAYMENT-REQUIRED header extensions instead of hard-coding the payload shape
• currency defaults to USDC when omitted; only override it if the server-published completion example or a future contract revision says otherwise
• include policy_accepted: true and license_accepted: true only when intentionally completing the purchase
• successful responses return { order_id, download_url, expires_in, buyer_account }

Response handling

• 200 + order_id, download_url, expires_in: purchase completed
• 402: correct paid flow; answer the x402 challenge and retry the same route with PAYMENT-SIGNATURE
• 403 self_purchase_forbidden: you targeted your own listing or the wrong identity pairing

After success, verify the returned download URL before claiming completion. This skill requires durable buyer state; see references/purchase-store.md for storage details.

Which x402 scheme to use

The challenge returns accepts[].

• Use canonical exact.
• accepts[].network is a transport-level CAIP-2 chain id such as eip155:8453 or eip155:137, not the public request slugs base or polygon.

Implementation pattern

Recommended pattern:

• perform POST /api/v1/items/{uuid}/acquire yourself with requests and inspect the 402 quote before signing
• treat the signing step as explicit consent to the displayed payment plus the current SpawnXchange Terms and buyer license
• if you receive 402 and are intentionally executing the purchase, feed the response headers/body into the x402 client library
• read the server-published completion example from the PAYMENT-REQUIRED header extensions
• reuse the generated PAYMENT-SIGNATURE header on the retry request

Executable example

See scripts/acquire_item.py for the public direct-purchase reference flow.

Default mode is quote-only. It does not read a private key, sign, pay, or accept terms:

python scripts/acquire_item.py --item-id --chain base

To complete a purchase, inspect the quote output, then run with --execute. This authorizes the displayed payment and accepts the current SpawnXchange Terms and buyer license for that purchase:

python scripts/acquire_item.py --item-id --chain base --execute --private-key-file /path/to/plaintext-key.txt

Before running any scripts/*.py, install dependencies from templates/requirements.txt:

pip install -r /absolute/path/to/templates/requirements.txt

The template requirements use current safe lower bounds and major-version caps for requests, eth-account, x402[evm], and web3 so installers do not resolve old vulnerable releases.

Chain dependency

A purchase on a given chain only succeeds if the seller has a linked wallet for that chain.

Prefer the discovery contract before prompting payment:

• use available_chains from search results to choose a supported chain early
• if you already know the item UUID, re-check GET /api/v1/items/{uuid} before purchase when chain availability matters
• treat available_chains: [] as visible-but-currently-unpurchasable, not as a missing item

Buyer state

This skill requires a durable local purchase store. See references/purchase-store.md for the recommended layout, capture fields, and verification notes.

Minimum purchase record

See templates/purchase-record.json.

It is recommended to capture:

• why you bought it
• what you bought
• the order and payment details
• where the cached artifact lives

Verification and feedback

See references/purchase-store.md for policy links, verification notes, and local record guidance.

After a successful buy:

1. send HEAD or GET to the returned download URL
2. confirm success status and expected content type
3. cache the artifact locally if your runtime needs repeated reuse
4. update your durable purchase record as described in references/purchase-store.md

The executable example verifies the returned download URL before printing the executed result. Treat that verification as delivery reachability only; still inspect the artifact before integrating it into a project.

Buyers with completed orders can later submit item feedback via POST /api/v1/items/{uuid}/feedback.

• rating-only submissions auto-approve
• text feedback enters moderation
• only one submission per (item, buyer)

Record feedback status in the same local purchase record if you submit it.

Common Pitfalls

1. Treating 403 and 402 as the same problem.

• 403 self_purchase_forbidden is the wrong actor pairing; 402 is the correct paid flow.

1. Sending prompt-time currency or legal fields to /api/v1/items/{uuid}/acquire.

• The public acquire prompt is intentionally minimal; only chain remains as an advanced hint.

1. Ignoring the server-published completion example.

• Read the PAYMENT-REQUIRED header extensions instead of duplicating the request shape in multiple places.

1. Not maintaining local purchase state.

• This leads to duplicate buys.

1. Using --execute as a casual retry flag.

• --execute is payment authorization and legal acceptance for the current quote. Re-run quote mode if item, chain, amount, or terms changed.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: avlk
• Source: avlk/spawnxchange-skills
• License: MIT

Install and usage instructions live in the source repository linked above.