Metronome vs Stripe API + MCP

Metronome

Metronome's API carries an Idempotency-Key on every POST, a public OpenAPI description of 142 operations, and agentic tokens whose writes wait for a person's approval. Prices for the Startup plan are public. Errors return only a message string, token scopes are set through support, and the status feed lists 13 incidents since 22 July 2026.

Stripe API + MCP

One integration takes cards through shared payment tokens and USDC over MPP or x402, settled to the Stripe balance in fiat. Card payments from agents have a 0.50 USD minimum, so per-call micropayments must use stablecoins.

Metronome

1. Send an Idempotency-Key header on every POST and reuse it on retry. A cached error is returned for the same key, so use a new key after fixing the cause
2. Give each usage event a stable transaction_id. Metronome ignores repeats for 34 days and accepts at most 100 events per /v1/ingest call
3. On 429 read X-Metronome-Rate-Limit-Type (client or customer) and back off. Unlisted endpoints default to 8 requests a second
4. With an agentic token, expect 403 AgenticMutationBlocked on writes. Post the original method, path and body to /v1/approval_requests and show the person the approval_url
5. Use a sandbox token for testing. The token alone decides whether a call reaches sandbox or production data

Stripe API + MCP

1. Switch to an Agent-tagged restricted key or OAuth before 31 October 2026; other keys get a 401
2. Call stripe_api_search and stripe_api_details before stripe_api_write to get the method and parameters right
3. When a write needs approval, give the person the URL and retry only after they approve; approvals expire after 24 hours
4. Send an Idempotency-Key on every create so a retry can't charge twice
5. On 429, read Stripe-Rate-Limited-Reason and back off with jitter; a 429 without it is a lock timeout