Agent Vault by Self vs Sponge Wallet

Agent Vault by Self

Scoped, revocable keys, OAuth on the hosted MCP server, spending caps, approvals and a documented threat model are designed to keep real card numbers and passwords out of the agent's context. The home page and launch post say cards are revealed only in an attested enclave, while the docs say that path is off on the hosted service.

Sponge Wallet

An agent can register a wallet with one unauthenticated call and pay x402 or MPP endpoints under daily, weekly and monthly limits enforced on Sponge's servers. No status page, rate limits, fee schedule, custody statement or security contact was found, the terms run to eleven short clauses, and the SDK was last published on 7 July 2026.

Agent Vault by Self

1. Pass the session handle from each hosted MCP result on every later call. Without it a page tool is refused or a new signed-out browser opens
2. On a pending answer, call get_pending_result with its wait id in the same turn. Repeating the original call starts a second one
3. Tell the user when waiting_on_owner is true. A first fill on a new site waits up to 15 minutes for the holder's approval
4. Before retrying a fill after an unknown outcome, check the merchant's order state or get_run_report. Some failures keep a recorded spend
5. Ask the holder to add an agent card to every card the agent may use. A card marked No limits accepts any amount on authorised sites

Sponge Wallet

1. Send Sponge-Version on every REST request. The skill file marks it required and the API answers with version status headers
2. Use evmTransfer and solanaTransfer, the helpers the docs describe as enforcing allowlists and spending limits, not plain transfer
3. Store the apiKey from registration at once. It is returned a single time, and losing it means registering again
4. Call GET /api/discover/{serviceId} before POST /api/paid/fetch. The skill file says direct service URLs fail with auth errors
5. Treat card details output as secret. It returns an encrypted card number and CVC with a one-time secret_key