API Knowledge

name: API Knowledge
description: API knowledge is the layer of indexes, descriptions, contexts, and signals that lets humans and agents reason
  about which APIs exist, what they do, who operates them, what they cost, how to call them, and how trustworthy they are.
  This topic repo catalogs the formats and platforms that publish API knowledge — APIs.json as a sitemap for an API project,
  APIs.guru as the community OpenAPI directory, RapidAPI Hub and the Postman Public API Network as commercial discovery surfaces,
  the OpenAPI Initiative as the spec authority, Jentic and Composio as agent-facing knowledge layers, llms.txt as a site-level
  guide for LLMs, schema.org/WebAPI as the structured-data vocabulary. Together they form a multi-source view of the API knowledge
  an AI agent needs to do real work against the API economy.
url: https://github.com/api-evangelist/knowledge
humanURL: https://apievangelist.com
image: ''
tags:
- API Knowledge
- Knowledge Graphs
- API Discovery
- API Search
- Catalogs
- Indexes
- Registries
- RAG
- Semantic Web
- JSON-LD
- LLMs
- AI Agents
- Topic
created: '2026-05-22'
modified: '2026-05-22'
specificationVersion: '0.20'
type: Index
apis:
- name: APIs.json
  description: APIs.json is an open-source machine-readable format for indexing the surface area of an API project — its operations,
    OpenAPI files, JSON Schema, JSON-LD contexts, documentation, pricing, status page, and maintainer contacts. It functions
    as a sitemap.xml for APIs and is the structural backbone of every repository in the API Evangelist network. The current
    stable revision is 0.20 with a 0.21 draft in flight.
  humanURL: https://apisjson.org
  baseURL: ''
  tags:
  - Index
  - Discovery
  - Catalog
  - Specification
  properties:
  - type: Documentation
    url: https://apisjson.org
  - type: GitHubRepository
    url: https://github.com/apis-json/api-specification
  - type: Versioning
    url: https://apisjson.org
- name: APIs.guru OpenAPI Directory
  description: APIs.guru is the community-driven directory of OpenAPI 2.0 and 3.x definitions for publicly available APIs.
    As reported on the api.apis.guru metrics endpoint, the directory currently indexes 2,529 APIs across 677 providers, with
    3,992 specifications and 108,837 endpoints. It exposes both an HTML browse experience and a REST API at api.apis.guru
    so that other tooling can pull live OpenAPI definitions on demand.
  humanURL: https://apis.guru
  baseURL: https://api.apis.guru/v2
  tags:
  - OpenAPI
  - Directory
  - Catalog
  - Community
  properties:
  - type: Portal
    url: https://apis.guru
  - type: GitHubRepository
    url: https://github.com/APIs-guru/openapi-directory
  - type: APIReference
    url: https://api.apis.guru/v2/list.json
  - type: Documentation
    url: https://github.com/APIs-guru/openapi-directory#readme
- name: RapidAPI Hub
  description: RapidAPI Hub is a commercial API marketplace and developer portal that acts as a discovery, onboarding, and
    metering layer over thousands of third-party APIs. RapidAPI Hub fronts a single key, single billing relationship, and
    a normalized "Try it" experience across the catalog. It is the canonical example of a commercial API knowledge surface
    aimed at developers rather than agents.
  humanURL: https://rapidapi.com/hub
  tags:
  - Marketplace
  - Hub
  - Discovery
  - Commercial
  properties:
  - type: Portal
    url: https://rapidapi.com/hub
  - type: Documentation
    url: https://docs.rapidapi.com
- name: Postman Public API Network
  description: The Postman Public API Network is Postman's public-facing index of API workspaces, collections, and environments.
    Postman's "Explore" surface organizes the network by category (App Security, Artificial Intelligence, Payments, etc.)
    and is the largest aggregator of executable API artifacts in collection form. It is the dominant collection-format counterpart
    to APIs.guru's OpenAPI directory.
  humanURL: https://www.postman.com/explore
  tags:
  - Collections
  - Discovery
  - Workspaces
  - Commercial
  properties:
  - type: Portal
    url: https://www.postman.com/explore
  - type: Documentation
    url: https://learning.postman.com
- name: OpenAPI Initiative
  description: The OpenAPI Initiative (OAI) is the Linux Foundation working group that stewards the OpenAPI Specification
    — the de-facto contract format for HTTP APIs and the substrate underneath most API knowledge tooling. OpenAPI 3.2.0 was
    released on 19 September 2025 and is the version currently advertised at spec.openapis.org/oas/latest.html. OAI also runs
    learn.openapis.org as a knowledge surface for the spec itself.
  humanURL: https://www.openapis.org
  tags:
  - Standard
  - OpenAPI
  - Specification
  - Linux Foundation
  properties:
  - type: Portal
    url: https://www.openapis.org
  - type: Documentation
    url: https://spec.openapis.org/oas/latest.html
  - type: GitHubOrganization
    url: https://github.com/OAI
  - type: Training
    url: https://learn.openapis.org
- name: Jentic
  description: Jentic is a governed execution layer that lets AI agents call enterprise APIs safely. It describes API workflows
    using the Arazzo open standard on top of OpenAPI, validates agent behavior in a sandbox, and converts successful interactions
    into deterministic, replayable workflows. Jentic is one of the clearest examples of agent-facing API knowledge that is
    both descriptive (what the API is) and operational (how to call it safely).
  humanURL: https://jentic.com
  tags:
  - Agents
  - Arazzo
  - Workflows
  - Governance
  properties:
  - type: Portal
    url: https://jentic.com
  - type: Documentation
    url: https://docs.jentic.com
- name: Composio
  description: Composio is an agent integration platform that exposes 1,000+ third-party applications as agent-ready tools.
    Composio publishes a tool registry accessed through session.tools() and ships both an OpenAPI-based native tool representation
    and an MCP-formatted surface for broader client compatibility. It is the dominant commercial "knowledge plus auth plus
    execution" layer aimed at agent builders.
  humanURL: https://composio.dev
  tags:
  - Agents
  - Tools
  - MCP
  - Integrations
  properties:
  - type: Portal
    url: https://composio.dev
  - type: Documentation
    url: https://docs.composio.dev
- name: llms.txt
  description: llms.txt is a community specification for a markdown file placed at the root path /llms.txt that gives LLMs
    a curated, link-rich entry point to a site's most important content. The spec is the lightest-weight form of API knowledge
    — it does not describe the API contract, but it enables an agent crawling a developer portal to find the docs, reference,
    and changelog without parsing the whole site. Early adopters include the FastHTML project and Answer.AI / fast.ai's nbdev
    sites.
  humanURL: https://llmstxt.org
  tags:
  - LLM
  - Knowledge
  - Markdown
  - Discovery
  properties:
  - type: Portal
    url: https://llmstxt.org
  - type: GitHubRepository
    url: https://github.com/AnswerDotAI/llms-txt
- name: schema.org WebAPI
  description: schema.org/WebAPI is the structured-data vocabulary for describing an "application programming interface accessible
    over Web/Internet technologies." It inherits from schema.org/Service and contributes properties like documentation, provider,
    termsOfService, name, description, and url. WebAPI is the canonical way to embed machine-readable knowledge about an API
    into a web page so that search engines and agents can pick it up via JSON-LD.
  humanURL: https://schema.org/WebAPI
  tags:
  - Vocabulary
  - Schema.org
  - JSON-LD
  - Semantic Web
  properties:
  - type: Documentation
    url: https://schema.org/WebAPI
common:
- type: Portal
  url: https://github.com/api-evangelist/knowledge
- type: GitHubRepository
  url: https://github.com/api-evangelist/knowledge
- type: Vocabulary
  url: vocabulary/knowledge-vocabulary.yml
- type: JSONLD
  url: json-ld/knowledge-context.jsonld
- type: JSONSchema
  url: json-schema/knowledge-record-schema.json
- type: Features
  data:
  - name: Multi-Source Aggregation
    description: An API knowledge record can cite multiple authoritative sources (APIs.json, APIs.guru, RapidAPI Hub, Postman,
      the provider's own portal) for the same provider, with per-source evidence and timestamps.
  - name: Capability Modeling
    description: Knowledge records describe not only the existence of an API but the capability it offers — what operations,
      what data, what workflows — so that agents can match intent to a callable surface.
  - name: Evidence and Provenance
    description: Every claim in an API knowledge record carries a source URL, a timestamp, and an optional verbatim quote,
      so downstream consumers can trust or re-verify the claim.
  - name: Source-of-Truth Hierarchy
    description: Records mark a primary source of truth (typically the provider's own OpenAPI or developer portal) and rank
      derivative indexes below it for conflict resolution.
  - name: Semantic Alignment
    description: Each record is published with a JSON-LD context that aligns its terms to schema.org/WebAPI, schema.org/Organization,
      and the APIs.json namespace so that knowledge can be linked across the web.
  - name: Agent-Readable Index
    description: The knowledge layer is designed to be consumed by AI agents as a retrieval surface — for RAG over API documentation,
      for tool selection in MCP hosts, and for capability lookup in agent frameworks like Jentic and Composio.
- type: UseCases
  data:
  - name: API Discovery
    description: A developer or agent searches across APIs.guru, RapidAPI Hub, and the Postman Network simultaneously to find
      an API that exposes a desired capability.
  - name: RAG Over API Documentation
    description: A retrieval-augmented agent indexes a provider's OpenAPI, llms.txt, and developer portal, then answers questions
      like "how do I authenticate" with source-cited responses.
  - name: Tool Selection for Agents
    description: An MCP host or agent framework uses a knowledge record to pick the right tool from a catalog of thousands,
      given an intent and a policy budget.
  - name: API Provider Intelligence
    description: An analyst joins APIs.guru entries with company hiring and investment signals to understand which companies
      are actively investing in APIs and which APIs are likely to be well-supported.
  - name: Knowledge-Driven Governance
    description: 'A platform team uses knowledge records to enforce policy: only APIs with a public OpenAPI, a published status
      page, and a documented rate-limit policy may be on-boarded.'
- type: Integrations
  data:
  - name: APIs.json + OpenAPI
    description: APIs.json points to one or more OpenAPI specs per API entry, tying the index format to the contract format.
  - name: APIs.guru + OpenAPI
    description: APIs.guru stores raw OpenAPI 2.0/3.x definitions and exposes them via a REST API.
  - name: Postman + Collections
    description: The Postman Network distributes executable Collection format artifacts that can be imported by any Postman
      client.
  - name: schema.org + JSON-LD
    description: Knowledge records embed schema.org/WebAPI types via JSON-LD so that search engines and agents can extract
      API descriptions from ordinary web pages.
  - name: Jentic + Arazzo
    description: Jentic describes API workflows in Arazzo and uses OpenAPI as the underlying operation contract.
  - name: Composio + MCP
    description: Composio exposes its tool registry as MCP servers in addition to its native OpenAPI-based tool format.
- type: Solutions
  data:
  - name: Open Indexes
    description: APIs.json and APIs.guru provide the open-source, free indexes of API surface area.
  - name: Commercial Marketplaces
    description: RapidAPI Hub and the Postman Public API Network monetize discovery and onboarding with metering, billing,
      and curation.
  - name: Agent-Facing Knowledge Layers
    description: Jentic and Composio convert API knowledge into agent-ready capabilities with auth, sandboxing, and policy.
  - name: Site-Level LLM Hints
    description: llms.txt and schema.org/WebAPI give every API provider a lightweight way to publish knowledge directly from
      their own site.
maintainers:
- FN: Kin Lane
  email: kinlane@gmail.com
  url: http://kinlane.com