Cello

Cello is an all-in-one, AI-powered referral platform for SaaS companies. It lets product teams embed in-product user referrals and run partner/affiliate programs with a few lines of code, then automates attribution, campaigns, notifications, fraud detection, and cross-border payouts. Cello ships an embeddable Referral Component and Attribution JS SDK for web plus native iOS, Android, Flutter, and React Native SDKs, a REST API for tokens, referral-code validation, events, and new-user rewards, a Growth Portal for analytics, and an official hosted MCP server exposing developer and growth-manager tools. Customers include Typeform, Miro, Descript, Pleo, and SmallPDF. Backed by HV Capital.

Cello publishes 5 API contracts indexed on the APIs.io network, including Events API, New Users API, Referral Codes API, and 2 more. Tagged areas include Company, Referral Marketing, Affiliate Marketing, Growth, and Software-as-a-Service.

The Cello catalog on APIs.io includes 1 Spectral governance ruleset.

Cello’s developer surface includes authentication, documentation, API reference, getting-started guide, support, engineering blog, pricing, and 33 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

62.2/100 strong ▬ flat Agent 60/100 agent ready Front door AI 3/6 light Heartbeat 96/100 alive saas Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

AccessFreemiumSelf serve

1 published contract 1 MCP Servers 3 Agent Skills

Company Referral Marketing Affiliate Marketing Growth Software-as-a-Service Attribution Partner Programs Ai Enterprise Software A2A

Kin Score

Kin Score How this is scored →
scored 2026-11-06 · rubric v0.27.0

Composite quality — 62.2/100 · strong

Contract Quality 9.6 / 19

Developer Ergonomics 11.8 / 15

Access Clarity 12.8 / 15

Operational Transparency 1.8 / 10

Contract Governance 2.9 / 9

Discoverability 5.6 / 8

Regulatory Posture 5.9 / 15

Create-or-Update Ergonomics 0.0 / 10

Agent readiness — 60/100 · 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 8 / 8

Request/Response Examples 7 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 0 / 6

Agent Skills 5 / 5

Well-Known Catalog 0 / 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 5 / 5

Registration Without a Human 6 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

Regulatory Posture applies to this provider. Its tags matched the Horizontal (data, software, accessibility, platform) 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/.

Show this score on your site.

It updates itself when the score changes. Paste this where you link to your API docs:

<a href="https://apis.io/providers/cello/"><img src="https://apis.io/badge/cello/card.svg" alt="Cello on APIs.io — Kin Score by API Evangelist"></a>

Other styles, a README pill and a shields.io endpoint are on the badge page.

Raise your score.

Agent readiness — checks not met, largest first (exact, from this profile):

Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented)
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0
Typed Event Surface +6 pts — AsyncAPI document, OR webhooks/callbacks objects in the as-published OpenAPI, OR common[].type includes Webhooks
Documented Reversibility +6 pts — a reversal operation in the contract, graded up when a window is documented too
Agentic Commerce Well-Known Document +5 pts — a parsing /.well-known/ucp.json or acp.json declaring a version and at least one service, OR (0.27) a live x402 payment challenge from _data/x402-adoption.json — `self` when its endpoints are on the provider's own domain, `platform` when they are on a vendor's
Dry-Run / Simulate Mode +4 pts — OpenAPI: destructive operations expose a dry_run / simulate / preview / validate_only parameter

2 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Contract Quality scores 51.1 — up to +12.2 composite points
Operational Transparency scores 18.4 — up to +10.6 composite points
Contract Governance scores 31.8 — up to +8.2 composite points

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

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 the provider profile at artifacts.apis.io/cello/apis.yml: open an issue on github.com/api-evangelist/cello to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Markets this provider is in provisional

The Kin Score Market layer reads a provider inside its market: its position, and how deep its integrations go. Depth is only comparable within a position. Provisional and unweighted: not part of the Kin Score or agent readiness.

Market	Position	Depth	Registered MCP server	Declares compatibility
Official SDKs on Packagist, pub.dev and Hex	distribution	19.2 (thin)	1	1

Registered MCP server and declares compatibility are report only — not weighted. Undeclared means we found nothing we can read, so there is no number: we never infer integrations.

Standards implemented 7

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

Agent2Agent

tagged — the provider's own APIs.json carries the standard as a tag; implementation not verified

Model Context Protocol (MCP)

measured — observed by APIs.io (verified)

Agent Skills

measured — observed by APIs.io (published)

OAuth 2.0 Protected Resource Metadata

measured — observed by APIs.io (verified)

Dynamic Client Registration

measured — observed by APIs.io (published)

OpenAPI

measured — observed by APIs.io (published)

OAuth 2.0

measured — observed by APIs.io (declared)

APIs 5

Individual APIs this provider publishes, each with its own machine-readable definition.

Cello Events API

The Events API from Cello — 1 operation(s) for events.

Cello New Users API

The New Users API from Cello — 1 operation(s) for new users.

Cello Referral Codes API

The Referral Codes API from Cello — 2 operation(s) for referral codes.

Cello Referrers API

The Referrers API from Cello — 1 operation(s) for referrers.

Cello Token API

The Token API from Cello — 1 operation(s) for token.

Open Collections 5

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

Cello Events API

OPEN COLLECTION

Cello Events New Users API

OPEN COLLECTION

Cello Events Referral Codes API

OPEN COLLECTION

Cello Events Referrers API

OPEN COLLECTION

Cello Events Token API

OPEN COLLECTION

MCP Servers 1

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

Cello MCP Server

Remote MCP server at mcp.cello.so over HTTP requiring OAuth; 8 tools listed.

MCP SERVER

Agent Skills 3

Packaged agent skills for driving this provider's APIs from an AI assistant.

Fetch a share link and check referee reward eligibility

AGENT SKILL

Cello

AGENT SKILL

Track a referral conversion with Cello

AGENT SKILL

Cello API pricing

Prices published by Cello, read 2026-10-28 from cello.so/pricing/.

Plan	Price
Start (User referrals)	$65/mth Includes: Up to $10K referral ARR, unlimited referrals, 1 campaign, all integrations & features, Slack support
Grow (User referrals)	$200/mth Includes: Up to $50K referral ARR, unlimited referrals, unlimited campaigns, priority Slack support, dedicated
Scale (User referrals)	$750/mth Includes: Up to $100K referral ARR, unlimited campaigns, custom SLAs
Enterprise (User referrals)	Custom/mth Includes: Unlimited referral ARR, unlimited campaigns, custom SLAs
Free (Partner referrals)	$0/mth Includes: 1 partner campaign, 5 transacting partners, 0% currency conversion costs
Plus (Partner referrals)	$80/mth Includes: 3 partner campaigns, 25 transacting partners, priority Slack support
Pro (Partner referrals)	$280/mth Includes: 10 partner campaigns, 100 transacting partners, custom SLAs
Enterprise (Partner referrals)	Custom/mth Includes: Unlimited partner campaigns, unlimited partners, custom SLAs

Plan details, limits and sources →

Billed by: subscription · FinOps profile →

Pricing Plans 2

Published pricing tiers and plan structures.

Cello Plans Pricing

8 plans

PLANS

Cello Price Estimates

0 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Cello Rate Limits

0 limits

RATE LIMITS

Service Levels 1

Uptime the provider promises or reports, as SLA4OAI. Read from its own pages; APIs.io runs no monitors.

Cello

SLA

FinOps 1

Cost, billing, and metering signals for API financial operations.

Cello Finops

FINOPS

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

Cello API Rules

58 rules · 54 errors 2 warnings 2 info

SPECTRAL

OpenAPI Overlays 1

Overlays applied on top of this provider's contracts. Each card says who wrote it: a document the provider publishes, or one API Evangelist derived or generated.

Cello Openapi Overlay

7 actions · documentation · cello-openapi-original.json

DERIVED

Security Posture 2

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

Cello Authentication

http/oauth2 · 3 schemes

SECURITY

Cello Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Scopes 1

OAuth scopes governing access to this provider's APIs.

Cello Scopes

2 scopes

SCOPES

Agentic Access 1

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

Cello Agentic Access

6 operations · 3 acting

AGENTIC

Resources

Get Started 4

Portal, sign-up, and the first successful call

DeveloperPortal

DeveloperPortal

GettingStarted

GettingStarted

Login

Sandbox

Sandbox

Documentation 2

Reference material describing how the API behaves

Documentation

Documentation

APIReference

APIReference

Agent Surfaces 7

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

MCPServer

LLMsTxt

AgentSkill

AgentSkill

AgentSkill

WellKnown

Scroll for all 7

Design & Contract 6

Pagination, idempotency, versioning, errors, and events

Components

Lifecycle

Conventions

ErrorCatalog

DataModel

Conformance

Build 4

SDKs, sample code, and the tooling you integrate with

GitHubOrganization

Packages

SDKs

ToolCrosswalk

Access & Security 4

Authentication, authorization, and security posture

DomainSecurity

Authentication

Compliance

OAuthScopes

Operate 4

Status, limits, changes, and where to get help

Support

ChangeLog

RateLimits

Contact

Commercial 4

Pricing, plans, and the legal terms of use

Pricing

TermsOfService

PrivacyPolicy

Plans

Company 3

The organization behind the API

BlogRSS

BlogRSS

Website

Website

Blog

Blog

Other 2

Properties that don't map to a standard resource type

Overlay

Overlay

AgentCard

AgentCard

Source (apis.yml)

aid: cello
name: Cello
description: Cello is an all-in-one, AI-powered referral platform for SaaS companies. It lets product teams embed in-product
  user referrals and run partner/affiliate programs with a few lines of code, then automates attribution, campaigns, notifications,
  fraud detection, and cross-border payouts. Cello ships an embeddable Referral Component and Attribution JS SDK for web plus
  native iOS, Android, Flutter, and React Native SDKs, a REST API for tokens, referral-code validation, events, and new-user
  rewards, a Growth Portal for analytics, and an official hosted MCP server exposing developer and growth-manager tools. Customers
  include Typeform, Miro, Descript, Pleo, and SmallPDF. Backed by HV Capital.
url: https://raw.githubusercontent.com/api-evangelist/cello/refs/heads/main/apis.yml
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
accessModel:
  pricing: freemium
  onboarding: self-serve
  trial: false
  try_now: false
  public: false
  label: Self-serve signup
  confidence: high
  source:
  - authentication
  - plans
  generated: '2026-08-13'
  method: searched
  note: List pricing is published for both product lines. Partner Referrals has a $0/mo Free tier (1 campaign, 10 partners);
    User Referrals starts at $200/mo and is metered on referral ARR, not API calls. No tier gates API, SDK or MCP access.
image: https://cello.so/wp-content/uploads/2022/12/Group-174900-1.png
x-type: company
x-source: vc-portfolio
x-backed-by:
- hv-capital
x-tier: stub
x-tier-reason: portfolio-lead
specificationVersion: '0.23'
created: '2026-07-17'
modified: '2026-10-06'
x-docs-platform: mintlify
x-docs-platform-confidence: medium
x-docs-platform-checked: 2026-09-21
x-docs-hosting: vercel
tags:
- Company
- Referral Marketing
- Affiliate Marketing
- Growth
- Software-as-a-Service
- Attribution
- Partner Programs
- Ai Enterprise Software
- A2A
tags_raw:
- Company
- Referral Marketing
- Affiliate Marketing
- Growth
- SaaS
- Attribution
- Partner Programs
- Ai Enterprise Software
- A2A
apis:
- aid: cello:cello-events-api
  name: Cello Events API
  description: The Events API from Cello — 1 operation(s) for events.
  humanURL: https://docs.cello.so/api-reference/introduction
  baseURL: https://api.cello.so
  tags:
  - Event
  tags_raw:
  - Events
  properties:
  - type: OpenAPI
    url: openapi/cello-events-api-openapi.yml
- aid: cello:cello-new-users-api
  name: Cello New Users API
  description: The New Users API from Cello — 1 operation(s) for new users.
  humanURL: https://docs.cello.so/api-reference/introduction
  baseURL: https://api.cello.so
  tags:
  - New Users
  properties:
  - type: OpenAPI
    url: openapi/cello-new-users-api-openapi.yml
- aid: cello:cello-referral-codes-api
  name: Cello Referral Codes API
  description: The Referral Codes API from Cello — 2 operation(s) for referral codes.
  humanURL: https://docs.cello.so/api-reference/introduction
  baseURL: https://api.cello.so
  tags:
  - Referral Codes
  properties:
  - type: OpenAPI
    url: openapi/cello-referral-codes-api-openapi.yml
- aid: cello:cello-referrers-api
  name: Cello Referrers API
  description: The Referrers API from Cello — 1 operation(s) for referrers.
  humanURL: https://docs.cello.so/api-reference/introduction
  baseURL: https://api.cello.so
  tags:
  - Referrers
  properties:
  - type: OpenAPI
    url: openapi/cello-referrers-api-openapi.yml
- aid: cello:cello-token-api
  name: Cello Token API
  description: The Token API from Cello — 1 operation(s) for token.
  humanURL: https://docs.cello.so/api-reference/introduction
  baseURL: https://api.cello.so
  tags:
  - Tokens
  tags_raw:
  - Token
  properties:
  - type: OpenAPI
    url: openapi/cello-token-api-openapi.yml
common:
- url: https://cello.so/feed/
  type: BlogRSS
- type: Website
  url: https://www.cello.so/
- type: Overlay
  url: overlays/cello-openapi-overlay.yaml
- type: DomainSecurity
  url: security/cello-domain-security.yml
- type: AgenticAccess
  url: agentic-access/cello-agentic-access.yml
- type: Authentication
  url: authentication/cello-authentication.yml
- type: DeveloperPortal
  url: https://docs.cello.so
- type: Documentation
  url: https://docs.cello.so
- type: APIReference
  url: https://docs.cello.so/api-reference/introduction
- type: GettingStarted
  url: https://docs.cello.so/integration-overview
- type: Support
  url: https://docs.cello.so/guides/support/faqs
- type: Blog
  url: https://cello.so/resources/
- type: GitHubOrganization
  url: https://github.com/getcello
- type: Pricing
  url: https://cello.so/pricing/
- type: Login
  url: https://portal.cello.so
- type: TermsOfService
  url: https://cello.so/terms-of-service/
- type: PrivacyPolicy
  url: https://cello.so/privacy-policy/
- type: MCPServer
  url: mcp/cello-mcp.yml
- type: LLMsTxt
  url: llms/cello-llms.txt
- type: Packages
  url: packages/cello-packages.yml
- type: SDKs
  url: packages/cello-packages.yml
- type: Components
  url: components/cello-components.yml
- type: Sandbox
  url: sandbox/cello-sandbox.yml
- type: ChangeLog
  url: changelog/cello-changelog.yml
- type: Lifecycle
  url: lifecycle/cello-lifecycle.yml
- type: Conventions
  url: conventions/cello-conventions.yml
- type: ErrorCatalog
  url: errors/cello-problem-types.yml
- type: DataModel
  url: data-model/cello-data-model.yml
- type: Conformance
  url: conformance/cello-conformance.yml
- type: Compliance
  url: https://cello.so/privacy-policy/
- type: AgentSkill
  url: skills/cello-track-referral-conversion.md
- type: AgentSkill
  url: skills/cello-fetch-and-reward-referee.md
- type: AgentSkill
  url: skills/cello-referral-integration.md
- type: AgentCard
  url: a2a/cello-a2a.yml
- type: WellKnown
  url: well-known/cello-well-known.yml
- type: OAuthScopes
  url: scopes/cello-scopes.yml
- type: ToolCrosswalk
  url: mcp/cello-tool-crosswalk.yml
- type: Plans
  url: plans/cello-plans-pricing.yml
- type: RateLimits
  url: rate-limits/cello-rate-limits.yml
- type: Contact
  url: mailto:support@cello.so
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
x-enrichment:
  date: '2026-08-13'
  status: enriched
  artifacts_added: 11
  pass: local-v1
x-a2a:
  verified: true
  probed: '2026-09-26'
  url: https://docs.cello.so/.well-known/agent-card.json
  grade: conformant
  protocol_version: '0.3'
  control: 404

Cello API — frequently asked questions

Does Cello have an API?

Yes. APIs.io lists 5 APIs from Cello, including Cello Events API, Cello New Users API and Cello Referral Codes API, and 2 more.

Is there an OpenAPI specification for the Cello API?

Yes. APIs.io indexes 5 OpenAPI specifications for Cello, each linked for download from this page.

How do I authenticate with the Cello API?

Cello documents its authentication (http/oauth2 · 3 schemes). The details are profiled on APIs.io as Cello Authentication.

How much does the Cello API cost?

Cello publishes its prices; its Start (User referrals) plan is $65/mth as of 2026-10-28. APIs.io lists 8 pricing plans for Cello, with each plan's price, limits and inclusions under Pricing on this page.

Does Cello have an MCP server?

Yes. APIs.io lists 1 MCP server for Cello: Remote MCP server at mcp.cello.so over HTTP requiring OAuth; 8 tools listed.

Is the Cello API ready for AI agents?

Cello has a Kin Score of 62.2 out of 100 (strong) and an Agent Readiness score of 59.9 (agent-ready), scored by API Evangelist on 2026-11-06.

Work with this as data

Every provider here is available over the APIs.io API and to AI agents over MCP.

MCP server

One button, every client — Claude, Cursor, VS Code and the rest.

https://apis.io/mcp

Tools for providers

9 MCP tools reach this

find_providersBrowse and filter every provider in the catalog.
get_provider_artifactsEvery artifact this provider publishes, grouped by type.
get_provider_operationsEvery operation across all of their OpenAPIs — one call instead of parsing every spec.
get_provider_toolsEvery MCP tool they ship, with the operation each wraps.
get_provider_evidenceHow each part of their score was established. Free — the basis for a claim should not sit behind it.
get_provider_ratingPRO — composite, band, trend and facet scores.
apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
resolveTurn a domain, URL or GitHub org into the provider it belongs to.
find_cohortsEvery scored population of providers in the catalog.

All 92 tools →

Call it yourself

curl for this page

This provider

curl "https://apis.io/api/v1/providers/cello"

All providers

curl "https://apis.io/api/v1/providers?limit=25"

Every operation they expose

curl "https://apis.io/api/v1/providers/cello/operations?limit=25"

How their score was established

curl "https://apis.io/api/v1/providers/cello/evidence"

Calls without X-API-Key need no key. Calls with it need a paid plan — get a key.

Get an API key

Free tier, no form to fill in. Signing in shares your email address with us — we store it to create your key and to recognise you if you sign in with another provider. See our Privacy Policy and Terms.

GitHub Google LinkedIn

A second provider on the same verified email joins the account you already have.