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 21 more developer resources.

🌐 Visit website 📡 Source on GitHub

49.3/100 developing ▬ flat Agent 48/100 agent ready saas Full breakdown ↓
scored 2026-09-08 · rubric v0.20.0

AccessSelf serve

1 APIs 1 MCP Servers

Company Agent Payments AI Agents Wallets Cryptocurrency Payments Stablecoins x402 MPP Financial Infrastructure MCP Fintech Cards On-Ramp

Kin Score

Kin Score How this is scored →
scored 2026-09-08 · rubric v0.20.0

Composite quality — 49.3/100 · developing

Contract Quality 9.8 / 19

Developer Ergonomics 12.5 / 15

Access Clarity 5.1 / 15

Operational Transparency 0.3 / 10

Contract Governance 1.6 / 9

Discoverability 5.7 / 8

Regulatory Posture 8.2 / 15

Create-or-Update Ergonomics 0.0 / 10

Agent readiness — 48/100 · agent ready

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 0 / 6

MCP Server 12 / 12

Machine-Readable Auth 10 / 10

Idempotency 0 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 7 / 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

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 6 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 6 / 6

Agentic Commerce Well-Known Document 0 / 5

Regulatory Posture applies to this provider. Its tags matched the Payments regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics applies to this provider. This API accepts writes, so it carries 10 points of the composite. It is scored from the published contracts themselves: whether a caller can create-or-update in one call, whether the write accepts a key the caller already holds, and whether the response says which branch ran. Without that, every write needs a search-and-branch in front of it, and the first time that check is skipped a duplicate record is created. Scored against the observed mean rather than raw — a provider at the catalog average is unchanged by this facet, not penalised by it.

The six quality facets above are damped to 75 points between them, because the conditional facet above carries the other 25. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 75% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. 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. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

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

Open Collections 11

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

API Collection

OPEN COLLECTION

Sponge public Agents API

OPEN COLLECTION

Sponge public Agents Cards API

OPEN COLLECTION

Sponge public Agents Fiat API

OPEN COLLECTION

Sponge public Agents MPP API

OPEN COLLECTION

Sponge public Agents Payments API

OPEN COLLECTION

Sponge public Agents Secrets API

OPEN COLLECTION

Sponge public Agents Sponge Card API

OPEN COLLECTION

Sponge public Agents Trading API

OPEN COLLECTION

Sponge public Agents Transfers API

OPEN COLLECTION

Sponge public Agents Wallet API

OPEN COLLECTION

Scroll for all 11

Arazzo Workflows 2

Multi-step API workflows described with the Arazzo specification.

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 Server

Sponge publishes official, hosted (remote) MCP servers for both the agent Wallet and the merchant Gateway. Wallet servers authenticate with an agent API key (sponge_live_...) fo...

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

SCOPES

Agentic Access 1

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

Sponge Agentic Access

57 operations · 33 acting

AGENTIC

Resources

Get Started 4

Portal, sign-up, and the first successful call

DeveloperPortal

GettingStarted

SignUp

Sandbox

Documentation 1

Reference material describing how the API behaves

Documentation

Documentation

Agent Surfaces 5

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

MCPServer

LLMsTxt

WellKnown

AgentSkill

Design & Contract 6

Pagination, idempotency, versioning, errors, and events

Conventions

Conformance

DataModel

Lifecycle

Arazzo

Arazzo

Build 4

SDKs, sample code, and the tooling you integrate with

GitHubOrganization

Packages

SDKs

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

Other 1

Properties that don't map to a standard resource type

Overlay

Overlay

Source (apis.yml)

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
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: true
  label: Hosted service · you call their endpoint
  confidence: high
  source:
  - openapi
  - pricing
  generated: '2026-08-28'
  method: derived
specificationVersion: '0.23'
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
- On-Ramp
tags_raw:
- 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:
  - Wallets
  tags_raw:
  - 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: Overlay
  url: overlays/sponge-openapi-overlay.yaml
- 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

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