Agentcard vs Crossmint API + Docs MCP

Agentcard

Purchases need the user's passkey approval by default, cards carry spending rules, and card creation takes an idempotency key. No status page, published rate limits beyond the token endpoint, or privacy policy of Agentcard's own was found, and the Trust Centre could not be read. Issuing costs $5,000 a month.

Crossmint API + Docs MCP

Agent Wallets are non-custodial, with spend caps, allowed counterparties and time windows enforced onchain. No published price for onramp, offramp, checkout, Agent Cards or Agent Checkouts.

Agentcard

1. Mint a platform token with POST /api/v2/oauth/token and cache it for its one hour. The endpoint allows 30 requests per 5 minutes per IP
2. Send the same Idempotency-Key on every retry of POST /api/v2/cards, and the same idempotency_key on every retry of buy_checkout
3. Pass source: "issued" to the MCP create_card tool for a card number. Without it the tool may start Vault setup and return a link
4. Call get_card_details only at the payment form and never log the result. Each read notifies the member and may return approval_required
5. Treat transaction.authorized and order.* webhooks as the record of a payment, and deduplicate deliveries on the event id

Crossmint API + Docs MCP

1. Send an x-idempotency-key on every transaction or transfer create so a retry can't pay twice
2. Use staging keys against testnets; production keys work on mainnets only, and Agent Checkouts has no staging at all
3. On 429, wait and retry. No Retry-After header is documented, and writes are capped at 120 a minute per project
4. Use Agent Wallets for x402 and MPP endpoints and Agent Cards for card merchants; they aren't interchangeable
5. Append .md to any docs URL for a Markdown copy