Onto

Onto provides a platform that makes website content readable to AI agents by serving clean Markdown at the same URLs. It offers a Read API, an MCP server, and tools for indexing, training data collection, and AI search integration. Free tier includes 1,000 credits per month with no credit card required. The service helps improve AI citation accuracy and reduces hallucinations by providing agents with exact page content.

Onto publishes 7 API contracts indexed on the APIs.io network, including Batch API, Extract API, Map API, and 4 more. Tagged areas include Artificial Intelligence, Content, Markdown, Read API, and Platform.

The Onto catalog on APIs.io includes 1 JSON-LD context and 1 Spectral governance ruleset.

Onto’s developer surface includes authentication, pricing, changelog, engineering blog, getting-started guide, documentation, API reference, and 22 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

46.4/100 developing Agent 45/100 agent ready Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

AccessFreemiumOpen⚡ Free to try

1 published contract 1 Agent Skills

Artificial Intelligence Content Markdown Read API Platform

Kin Score

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

Composite quality — 46.4/100 · developing

Contract Quality 14.5 / 21

Developer Ergonomics 5.0 / 17

Access Clarity 9.2 / 17

Operational Transparency 1.7 / 11

Contract Governance 2.2 / 10

Discoverability 5.6 / 9

Regulatory Posture 3.7 / 15

Agent readiness — 45/100 · agent ready

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 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 could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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

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

MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship
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

3 more unmet checks in the Agent Readiness table above.

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

Developer Ergonomics scores 29.2 — up to +14.2 composite points
Operational Transparency scores 15.8 — up to +10.9 composite points
Contract Governance scores 22.0 — up to +9.4 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/buildonto-dev/apis.yml: open an issue on github.com/api-evangelist/buildonto-dev 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 →

Standards implemented 3

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.

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)

APIs 7

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

Onto Batch API

Read, score, or extract up to 50 URLs (a list or a whole site) in one call.

Onto Extract API

Return the structured data a page declares (JSON-LD, OpenGraph, meta). Deterministic, no AI.

Onto Map API

Discover a site's URLs via sitemap, then links — without reading them.

Onto Read API

Fetch and clean public URLs into agent-ready Markdown.

Onto Read + Score API

One call, both outputs — Markdown plus the scoring metadata.

Onto Score API

Run the AIO scorer on a URL — returns 0–100 score, penalties, benefits, recommendations.

Onto Usage API

Plan quota, concurrent-slot state, and credit balance.

Scroll for all 7

Agent Skills 1

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

read-url

AGENT SKILL

Onto API pricing

Prices published by Onto, read 2026-11-03 from buildonto.dev/pricing.

Plan	Price
Read Free	$0 forever
Read Starter	$9/ month
Read Growth	$49/ month
Read Scale	$250/ month
Serve Free	$0 forever
Serve Pro	$19/ month
Serve Business	$99/ month
Serve Enterprise	Contact sales

Plan details, limits and sources →

Pricing Plans 1

Published pricing tiers and plan structures.

Buildonto Dev Plans Pricing

8 plans

PLANS

Semantic Vocabularies 1

JSON-LD contexts and semantic vocabularies used across these APIs.

Buildonto Dev Context

12 classes · 54 properties

JSON-LD

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

Onto API Rules

68 rules · 62 errors 2 warnings 4 info

SPECTRAL

JSON Schema 6

Standalone JSON Schema definitions for this provider's data models.

ReadAndScoreResponse

14 properties

JSON SCHEMA

ReadRequest

2 properties

JSON SCHEMA

ReadResponse

7 properties

JSON SCHEMA

ScoreRequest

1 properties

JSON SCHEMA

ScoreResponse

12 properties

JSON SCHEMA

UsageResponse

10 properties

JSON SCHEMA

Security Posture 3

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

Buildonto Dev Authentication

2 schemes

SECURITY

Buildonto Dev Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Buildonto Dev Vulnerability Disclosure

security.txt · contact published

SECURITY

Agentic Access 1

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

Buildonto Dev Agentic Access

7 operations · 6 acting

AGENTIC

Resources

Get Started 2

Portal, sign-up, and the first successful call

Login

GettingStarted

GettingStarted

Documentation 2

Reference material describing how the API behaves

Documentation

Documentation

APIReference

APIReference

Agent Surfaces 4

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgentSkill

LLMsTxt

WellKnown

Design & Contract 6

Pagination, idempotency, versioning, errors, and events

Spectral

JSONLD

Vocabulary

DataModel

ErrorCatalog

Conformance

Access & Security 5

Authentication, authorization, and security posture

Authentication

Authentication

SecurityTxt

SecurityTxt

Security

Security

VulnerabilityDisclosure

VulnerabilityDisclosure

DomainSecurity

DomainSecurity

Operate 2

Status, limits, changes, and where to get help

Roadmap

Roadmap

ChangeLog

ChangeLog

Commercial 4

Pricing, plans, and the legal terms of use

Plans

TermsOfService

PrivacyPolicy

Pricing

Company 2

The organization behind the API

Blog

Blog

Website

Website

Other 2

Properties that don't map to a standard resource type

Hosts

Hosts

Vendors

Vendors

Source (apis.yml)

aid: buildonto-dev
name: Onto
accessModel:
  pricing: freemium
  onboarding: open
  trial: false
  try_now: true
  public: true
  gated: none
  gated_source:
  - onboarding
  label: Freemium · Open access
  confidence: medium
  source:
  - plans
  - authentication
  - security
  generated: '2026-11-06'
  method: derived
image: https://buildonto.dev/opengraph-image.png?opengraph-image.789f9c1d.png
description: Onto provides a platform that makes website content readable to AI agents by serving clean Markdown at the same
  URLs. It offers a Read API, an MCP server, and tools for indexing, training data collection, and AI search integration.
  Free tier includes 1,000 credits per month with no credit card required. The service helps improve AI citation accuracy
  and reduces hallucinations by providing agents with exact page content.
url: https://artifacts.apis.io/buildonto-dev/apis.yml
x-type: company
x-source: harvest:mcp-registry
x-tier: profiled
x-tier-reason: enrichment pass 2026-11-03 (modular-v1; was harvest)
specificationVersion: '0.20'
created: '2026-11-03'
modified: '2026-11-03'
tags:
- Artificial Intelligence
- Content
- Markdown
- Read API
- Platform
tags_raw:
- AI
- Content
- Markdown
- ReadAPI
- Platform
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: AgenticAccess
  url: agentic-access/buildonto-dev-agentic-access.yml
- type: Plans
  url: plans/buildonto-dev-plans-pricing.yml
- type: Spectral
  url: rules/buildonto-dev-rules.yml
- type: JSONLD
  url: json-ld/buildonto-dev-context.jsonld
- type: Vocabulary
  url: vocabulary/buildonto-dev-vocabulary.yml
- type: AgentSkill
  url: skills/_index.yml
- type: DataModel
  url: data-model/buildonto-dev-data-model.yml
- type: Authentication
  url: authentication/buildonto-dev-authentication.yml
- type: ErrorCatalog
  url: errors/buildonto-dev-problem-types.yml
- type: Conformance
  url: conformance/buildonto-dev-conformance.yml
- type: LLMsTxt
  url: llms/buildonto-dev-llms.txt
- type: SecurityTxt
  url: well-known/buildonto-dev-security.txt
- type: WellKnown
  url: well-known/buildonto-dev-well-known.yml
- type: Hosts
  url: hosts/buildonto-dev-hosts.yml
- type: Vendors
  url: vendors/buildonto-dev-vendors.yml
- type: TermsOfService
  url: https://buildonto.dev/legal/terms
- type: Security
  url: https://buildonto.dev/legal/security
- type: Roadmap
  url: https://buildonto.dev/roadmap
- type: PrivacyPolicy
  url: https://buildonto.dev/legal/privacy
- type: Pricing
  url: https://buildonto.dev/pricing
- type: Login
  url: https://app.buildonto.dev/login
- type: ChangeLog
  url: https://buildonto.dev/changelog
- type: Blog
  url: https://buildonto.dev/blog
- type: GettingStarted
  url: https://docs.buildonto.dev/quickstart
- type: Documentation
  url: https://docs.buildonto.dev/
- type: APIReference
  url: https://docs.buildonto.dev/reference
- type: VulnerabilityDisclosure
  url: security/buildonto-dev-vulnerability-disclosure.yml
- type: DomainSecurity
  url: security/buildonto-dev-domain-security.yml
- type: Website
  url: https://buildonto.dev/
apis:
- aid: buildonto-dev:buildonto-dev-batch-api
  name: Onto Batch API
  description: Read, score, or extract up to 50 URLs (a list or a whole site) in one call.
  humanURL: https://docs.buildonto.dev/reference
  baseURL: https://api.buildonto.dev
  tags:
  - Batch
  properties:
  - type: OpenAPI
    url: openapi/buildonto-dev-batch-api-openapi.yml
  - type: JSONSchema
    url: json-schema/buildonto-dev-score-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-usage-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-and-score-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-request-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-score-request-schema.json
- aid: buildonto-dev:buildonto-dev-extract-api
  name: Onto Extract API
  description: Return the structured data a page declares (JSON-LD, OpenGraph, meta). Deterministic, no AI.
  humanURL: https://docs.buildonto.dev/reference
  baseURL: https://api.buildonto.dev
  tags:
  - Extract
  properties:
  - type: OpenAPI
    url: openapi/buildonto-dev-extract-api-openapi.yml
  - type: JSONSchema
    url: json-schema/buildonto-dev-score-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-usage-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-and-score-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-request-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-score-request-schema.json
- aid: buildonto-dev:buildonto-dev-map-api
  name: Onto Map API
  description: Discover a site's URLs via sitemap, then links — without reading them.
  humanURL: https://docs.buildonto.dev/reference
  baseURL: https://api.buildonto.dev
  tags:
  - Maps
  tags_raw:
  - Map
  properties:
  - type: OpenAPI
    url: openapi/buildonto-dev-map-api-openapi.yml
  - type: JSONSchema
    url: json-schema/buildonto-dev-score-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-usage-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-and-score-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-request-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-score-request-schema.json
- aid: buildonto-dev:buildonto-dev-read-api
  name: Onto Read API
  description: Fetch and clean public URLs into agent-ready Markdown.
  humanURL: https://docs.buildonto.dev/reference
  baseURL: https://api.buildonto.dev
  tags: []
  tags_raw:
  - Read
  properties:
  - type: OpenAPI
    url: openapi/buildonto-dev-read-api-openapi.yml
  - type: JSONSchema
    url: json-schema/buildonto-dev-score-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-usage-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-and-score-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-request-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-score-request-schema.json
- aid: buildonto-dev:buildonto-dev-read-score-api
  name: Onto Read + Score API
  description: One call, both outputs — Markdown plus the scoring metadata.
  humanURL: https://docs.buildonto.dev/reference
  baseURL: https://api.buildonto.dev
  tags:
  - Read + Score
  properties:
  - type: OpenAPI
    url: openapi/buildonto-dev-read-score-api-openapi.yml
  - type: JSONSchema
    url: json-schema/buildonto-dev-score-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-usage-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-and-score-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-request-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-score-request-schema.json
- aid: buildonto-dev:buildonto-dev-score-api
  name: Onto Score API
  description: Run the AIO scorer on a URL — returns 0–100 score, penalties, benefits, recommendations.
  humanURL: https://docs.buildonto.dev/reference
  baseURL: https://api.buildonto.dev
  tags:
  - Score
  properties:
  - type: OpenAPI
    url: openapi/buildonto-dev-score-api-openapi.yml
  - type: JSONSchema
    url: json-schema/buildonto-dev-score-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-usage-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-and-score-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-request-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-score-request-schema.json
- aid: buildonto-dev:buildonto-dev-usage-api
  name: Onto Usage API
  description: Plan quota, concurrent-slot state, and credit balance.
  humanURL: https://docs.buildonto.dev/reference
  baseURL: https://api.buildonto.dev
  tags:
  - Usage
  properties:
  - type: OpenAPI
    url: openapi/buildonto-dev-usage-api-openapi.yml
  - type: JSONSchema
    url: json-schema/buildonto-dev-score-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-usage-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-and-score-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-response-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-read-request-schema.json
  - type: JSONSchema
    url: json-schema/buildonto-dev-score-request-schema.json
x-enrichment:
  date: '2026-11-03'
  status: enriched
  artifacts_added: 37
  pass: modular-v1
  engine: identity=local,contract=local,surfaces=local,docs=local,regulatory=local

Onto API — frequently asked questions

Does Onto have an API?

Yes. APIs.io lists 7 APIs from Onto, including Onto Batch API, Onto Extract API and Onto Map API, and 4 more.

Is there an OpenAPI specification for the Onto API?

Yes. APIs.io indexes 7 OpenAPI specifications for Onto, each linked for download from this page.

How do I authenticate with the Onto API?

Onto documents its authentication (2 schemes). The details are profiled on APIs.io as Buildonto Dev Authentication.

How much does the Onto API cost?

Onto publishes its prices; its Read Free plan is $0 forever as of 2026-11-03. APIs.io lists 8 pricing plans for Onto, with each plan's price, limits and inclusions under Pricing on this page.

Is the Onto API ready for AI agents?

Onto has a Kin Score of 46.4 out of 100 (developing) and an Agent Readiness score of 45.1 (agent-ready), scored by API Evangelist on 2026-11-06.

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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.

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