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).

Sponge publishes 10 APIs on the APIs.io network, including Agents API, Cards API, Fiat API, and 7 more. Tagged areas include Company, Agent Payments, AI Agents, Wallets, and Cryptocurrency.

Sponge’s developer surface includes documentation, getting-started guide, support, signup flow, authentication, CLI, sandbox, and 20 more developer resources.

🌐 Visit website 📡 Source on GitHub
50.9/100 developing ▬ flat Agent 62/100 agent native Full breakdown ↓
scored 2026-07-27 · rubric v0.5
AccessSelf serve
10 APIs 1 MCP Servers
CompanyAgent PaymentsAI AgentsWalletsCryptocurrencyPaymentsStablecoinsx402MPPFinancial InfrastructureMCPFintechCardsOnramp

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-07-27 · rubric v0.5
Composite quality — 50.9/100 · developing
Contract Quality 13.3 / 25
Developer Ergonomics 15.7 / 20
Commercial Clarity 6.8 / 20
Operational Transparency 0.7 / 13
Governance 0.0 / 12
Discoverability 10.0 / 10
Agent readiness — 62/100 · agent native
Machine-Readable Contract 18 / 18
Agentic Access Contract 15 / 15
MCP Server 12 / 12
Machine-Readable Auth 10 / 10
Idempotency 0 / 9
Stable Error Semantics 0 / 8
Request/Response Examples 0 / 7
Rate-Limit Signaling 0 / 7
Typed Event Surface 0 / 6
Agent Skills 5 / 5
Well-Known Catalog 4 / 4
Consent & Bot Identity 0 / 3
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. This rating is computed from github.com/api-evangelist/sponge: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

APIs 10

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 for all 10

Arazzo Workflows 3

Multi-step API workflows described with the Arazzo specification.

_Index

ARAZZO

Sponge — create an agent and issue its key

Platform backend creates a new agent, then mints an agent API key for runtime use.

ARAZZO

Sponge — check balance, transfer, and confirm

Read wallet balances, send an EVM transfer, then poll transaction status.

ARAZZO

MCP Servers 1

Model Context Protocol servers that expose these APIs to AI agents.

sponge-mcp.yml

MCP SERVER

Security Posture 2

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Sponge Authentication

http/oauth2/openIdConnect · 4 schemes

SECURITY

Sponge Domain Security

TLSv1.3

SECURITY

Scopes 1

OAuth scopes governing access to this provider's APIs.

Sponge Scopes

5 scopes

5 scopes

SCOPES

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

Sponge Agentic Access

57 operations · 33 acting

57 operations · 33 acting

AGENTIC

Resources

Get Started 4

Portal, sign-up, and the first successful call

DeveloperPortal
DeveloperPortal
 GettingStarted
GettingStarted
 SignUp
SignUp
 Sandbox
Sandbox

Documentation 1

Reference material describing how the API behaves

Documentation
Documentation

Agent Surfaces 5

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess
AgenticAccess
 MCPServer
MCPServer
 LLMsTxt
LLMsTxt
 WellKnown
WellKnown
 AgentSkill
AgentSkill

Design & Contract 6

Pagination, idempotency, versioning, errors, and events

Conventions
Conventions
 Conformance
Conformance
 DataModel
DataModel
 Lifecycle
Lifecycle
 Arazzo
Arazzo
 Arazzo
Arazzo

Build 4

SDKs, sample code, and the tooling you integrate with

GitHubOrganization
GitHubOrganization
 Packages
Packages
 SDKs
SDKs
 CLI
CLI

Access & Security 3

Authentication, authorization, and security posture

Authentication
Authentication
 OAuthScopes
OAuthScopes
 DomainSecurity
DomainSecurity

Operate 1

Status, limits, changes, and where to get help

Support
Support

Commercial 2

Pricing, plans, and the legal terms of use

TermsOfService
TermsOfService
 PrivacyPolicy
PrivacyPolicy

Company 1

The organization behind the API

Website
Website

Source (apis.yml)

apis.yml Raw ↑ 
aid: sponge
name: Sponge
description: 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).
url: https://raw.githubusercontent.com/api-evangelist/sponge/refs/heads/main/apis.yml
x-type: company
x-source: vc-portfolio
x-backed-by:
- y-combinator
accessModel:
  pricing: unknown
  onboarding: self-serve
  trial: false
  try_now: false
  public: false
  label: Self-serve signup
  confidence: medium
  source:
  - authentication
  generated: '2026-07-22'
  method: derived
image: https://paysponge.com/logo.png
tags:
- Company
- Agent Payments
- AI Agents
- Wallets
- Cryptocurrency
- Payments
- Stablecoins
- x402
- MPP
- Financial Infrastructure
- MCP
- Fintech
- Cards
- Onramp
created: '2026-07-17'
modified: '2026-07-21'
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
apis:
- aid: sponge:sponge-agents-api
  name: Sponge Agents API
  description: The Agents API from Sponge — 5 operation(s) for agents.
  humanURL: https://docs.paysponge.com
  baseURL: https://api.wallet.paysponge.com
  tags:
  - Agents
  properties:
  - type: OpenAPI
    url: openapi/sponge-agents-api-openapi.yml
  - type: APIReference
    url: https://docs.paysponge.com/api-reference/public-openapi.json
- aid: sponge:sponge-cards-api
  name: Sponge Cards API
  description: The Cards API from Sponge — 6 operation(s) for cards.
  humanURL: https://docs.paysponge.com
  baseURL: https://api.wallet.paysponge.com
  tags:
  - Cards
  properties:
  - type: OpenAPI
    url: openapi/sponge-cards-api-openapi.yml
  - type: APIReference
    url: https://docs.paysponge.com/api-reference/public-openapi.json
- aid: sponge:sponge-fiat-api
  name: Sponge Fiat API
  description: The Fiat API from Sponge — 11 operation(s) for fiat.
  humanURL: https://docs.paysponge.com
  baseURL: https://api.wallet.paysponge.com
  tags:
  - Fiat
  properties:
  - type: OpenAPI
    url: openapi/sponge-fiat-api-openapi.yml
  - type: APIReference
    url: https://docs.paysponge.com/api-reference/public-openapi.json
- aid: sponge:sponge-mpp-api
  name: Sponge MPP API
  description: The MPP API from Sponge — 5 operation(s) for mpp.
  humanURL: https://docs.paysponge.com
  baseURL: https://api.wallet.paysponge.com
  tags:
  - MPP
  properties:
  - type: OpenAPI
    url: openapi/sponge-mpp-api-openapi.yml
  - type: APIReference
    url: https://docs.paysponge.com/api-reference/public-openapi.json
- aid: sponge:sponge-payments-api
  name: Sponge Payments API
  description: The Payments API from Sponge — 1 operation(s) for payments.
  humanURL: https://docs.paysponge.com
  baseURL: https://api.wallet.paysponge.com
  tags:
  - Payments
  properties:
  - type: OpenAPI
    url: openapi/sponge-payments-api-openapi.yml
  - type: APIReference
    url: https://docs.paysponge.com/api-reference/public-openapi.json
- aid: sponge:sponge-secrets-api
  name: Sponge Secrets API
  description: The Secrets API from Sponge — 2 operation(s) for secrets.
  humanURL: https://docs.paysponge.com
  baseURL: https://api.wallet.paysponge.com
  tags:
  - Secrets
  properties:
  - type: OpenAPI
    url: openapi/sponge-secrets-api-openapi.yml
  - type: APIReference
    url: https://docs.paysponge.com/api-reference/public-openapi.json
- aid: sponge:sponge-sponge-card-api
  name: Sponge Sponge Card API
  description: The Sponge Card API from Sponge — 7 operation(s) for sponge card.
  humanURL: https://docs.paysponge.com
  baseURL: https://api.wallet.paysponge.com
  tags:
  - Sponge Card
  properties:
  - type: OpenAPI
    url: openapi/sponge-sponge-card-api-openapi.yml
  - type: APIReference
    url: https://docs.paysponge.com/api-reference/public-openapi.json
- aid: sponge:sponge-trading-api
  name: Sponge Trading API
  description: The Trading API from Sponge — 1 operation(s) for trading.
  humanURL: https://docs.paysponge.com
  baseURL: https://api.wallet.paysponge.com
  tags:
  - Trading
  properties:
  - type: OpenAPI
    url: openapi/sponge-trading-api-openapi.yml
  - type: APIReference
    url: https://docs.paysponge.com/api-reference/public-openapi.json
- aid: sponge:sponge-transfers-api
  name: Sponge Transfers API
  description: The Transfers API from Sponge — 9 operation(s) for transfers.
  humanURL: https://docs.paysponge.com
  baseURL: https://api.wallet.paysponge.com
  tags:
  - Transfers
  properties:
  - type: OpenAPI
    url: openapi/sponge-transfers-api-openapi.yml
  - type: APIReference
    url: https://docs.paysponge.com/api-reference/public-openapi.json
- aid: sponge:sponge-wallet-api
  name: Sponge Wallet API
  description: The Wallet API from Sponge — 4 operation(s) for wallet.
  humanURL: https://docs.paysponge.com
  baseURL: https://api.wallet.paysponge.com
  tags:
  - Wallet
  properties:
  - type: OpenAPI
    url: openapi/sponge-wallet-api-openapi.yml
  - type: APIReference
    url: https://docs.paysponge.com/api-reference/public-openapi.json
common:
- type: Website
  url: https://paysponge.com
- type: DeveloperPortal
  url: https://docs.paysponge.com
- type: Documentation
  url: https://docs.paysponge.com
- type: GettingStarted
  url: https://docs.paysponge.com/wallet/sdk.md
- type: Support
  url: https://discord.gg/gwH2QqMDaX
- type: GitHubOrganization
  url: https://github.com/paysponge
- type: SignUp
  url: https://wallet.paysponge.com
- type: TermsOfService
  url: https://paysponge.com/terms
- type: PrivacyPolicy
  url: https://paysponge.com/privacy
- type: Authentication
  url: authentication/sponge-authentication.yml
- type: OAuthScopes
  url: scopes/sponge-scopes.yml
- type: DomainSecurity
  url: security/sponge-domain-security.yml
- type: AgenticAccess
  url: agentic-access/sponge-agentic-access.yml
- type: MCPServer
  url: mcp/sponge-mcp.yml
- type: LLMsTxt
  url: llms/sponge-llms.txt
- type: Packages
  url: packages/sponge-packages.yml
- type: SDKs
  url: packages/sponge-packages.yml
- type: CLI
  url: cli/sponge-cli.yml
- type: WellKnown
  url: well-known/sponge-well-known.yml
- type: Conventions
  url: conventions/sponge-conventions.yml
- type: Conformance
  url: conformance/sponge-conformance.yml
- type: DataModel
  url: data-model/sponge-data-model.yml
- type: Lifecycle
  url: lifecycle/sponge-lifecycle.yml
- type: Sandbox
  url: sandbox/sponge-sandbox.yml
- type: AgentSkill
  url: skills/_index.yml
- type: Arazzo
  name: Check balance, transfer, and confirm
  url: arazzo/sponge-transfer-and-confirm.yml
- type: Arazzo
  name: Create an agent and issue its key
  url: arazzo/sponge-agent-onboarding.yml
x-enrichment:
  date: '2026-07-21'
  status: enriched
  artifacts_added: 21
  pass: local-v1