Sponge
Sponge builds financial infrastructure for the agent economy — wallets that let AI agents hold and spend money, and a gateway that lets businesses sell services directly to agents. The Sponge Wallet API gives an agent its own multi-chain crypto wallet with balances, transfers, swaps, cross-chain bridges, payment links, cards (including a Rain-issued Visa Sponge Card), fiat onramps (Coinbase, Stripe), and trading on Hyperliquid and Polymarket, plus paid access to external services via the x402 and MPP agent-payment protocols. A TypeScript and Python SDK, a spongewallet CLI, and hosted MCP servers ship first-party. Backed by Y Combinator (W2026).
Real signal across most facets with visible, nameable gaps — the contract exists but is thin, or the portal is good while governance and commercial terms are absent.
API Evangelist profiles Sponge the way a machine reads it — 18 machine-readable artifacts across 10 APIs, pulled from the provider's own public surface and indexed so a developer, an analyst, or an AI agent can evaluate it against every other provider on the network.
Every provider in the network is reduced to the same set of machine-readable artifacts — OpenAPI contracts, event specifications, GraphQL schemas, runnable collections, pricing and rate-limit signals, security posture, OAuth scopes, and the agent surfaces (MCP servers and skills) that let software drive the API on its own. We profile them because the interface is the part of a company you can actually inspect: it is a truer signal of what a provider does than any marketing page. From those artifacts we compute the Kin Score — Sponge scores 50.9/100 (developing), with a separate agent-readiness read of 62/100 (agent native). The full breakdown is below, followed by every artifact we hold — each card links through to its machine-readable definition on apis.io.
Kin Score
This is the API Evangelist rating — a single, repeatable read computed from the artifacts on this page. Green fill is points earned; the red track is points possible, so every bar shows earned-versus-possible at a glance.
Kin Score
How this is scored →scored 2026-07-27 · rubric v0.5
How we profile Sponge
Each block below is one kind of artifact we hold for Sponge. For each we say what it is and why it earns a place in the profile, then list every one we've indexed — capped at two rows, scroll within the panel for the rest.
APIs 10
Each API is captured as its own OpenAPI definition — every operation, parameter, and response. This is the single most useful machine-readable description of what an API does, and it's what lets us score, lint, mock, and generate against it without asking the provider for anything.
Individual APIs this provider publishes, each with its own machine-readable definition.
Sponge Agents API
The Agents API from Sponge — 5 operation(s) for agents.
Sponge Cards API
The Cards API from Sponge — 6 operation(s) for cards.
Sponge Fiat API
The Fiat API from Sponge — 11 operation(s) for fiat.
Sponge MPP API
The MPP API from Sponge — 5 operation(s) for mpp.
Sponge Payments API
The Payments API from Sponge — 1 operation(s) for payments.
Sponge Secrets API
The Secrets API from Sponge — 2 operation(s) for secrets.
Sponge Sponge Card API
The Sponge Card API from Sponge — 7 operation(s) for sponge card.
Sponge Trading API
The Trading API from Sponge — 1 operation(s) for trading.
Sponge Transfers API
The Transfers API from Sponge — 9 operation(s) for transfers.
Sponge Wallet API
The Wallet API from Sponge — 4 operation(s) for wallet.
Scroll within the panel for all 10 ·
Arazzo Workflows 3
Real integrations are rarely a single call. Arazzo describes the multi-step sequences — auth, then create, then confirm — so both a human and an agent can follow the choreography, not just the endpoints.
Multi-step API workflows described with the Arazzo specification.
_Index
ARAZZOSponge — create an agent and issue its key
Platform backend creates a new agent, then mints an agent API key for runtime use.
ARAZZOSponge — check balance, transfer, and confirm
Read wallet balances, send an EVM transfer, then poll transaction status.
ARAZZOMCP Servers 1
Model Context Protocol servers expose these APIs directly to AI agents. We profile them because agent-native access is the fastest-growing way this provider's capabilities actually get used.
Model Context Protocol servers that expose these APIs to AI agents.
sponge-mcp.yml
MCP SERVERSecurity Posture 2
Authentication, domain security, vulnerability disclosure, and trust-center signals — the evidence that a provider takes security seriously enough to document it. We profile it because you can't govern what you can't see.
Authentication, domain security, vulnerability disclosure, and trust-center signals.
Scopes 1
OAuth scopes are the vocabulary of least-privilege access. Profiling them shows exactly what an integration — or an agent acting on a user's behalf — is allowed to do.
OAuth scopes governing access to this provider's APIs.
Agentic Access 1
An x-agentic-access contract marks which operations are safe for an agent to run on its own and which need a human in the loop. It is the difference between an API an agent can use and one it can use safely.
Recommended x-agentic-access execution contracts for AI agents.
Resources
Every other property we hold for Sponge — documentation, portals, status pages, policies, and corporate surface — grouped by the job it does, following the integrator's arc from getting started to running in production.
Get Started 4
Portal, sign-up, and the first successful call
Documentation 1
Reference material describing how the API behaves
Agent Surfaces 5
MCP servers, agent skills, and machine-readable catalogs
Design & Contract 6
Pagination, idempotency, versioning, errors, and events
Build 4
SDKs, sample code, and the tooling you integrate with
Access & Security 3
Authentication, authorization, and security posture
Operate 1
Status, limits, changes, and where to get help
Commercial 2
Pricing, plans, and the legal terms of use
Company 1
The organization behind the API
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