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, and Naftiko Signals as a company-and-investment intelligence
  layer that complements the spec-driven catalogs. 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: Naftiko Signals
    description: >-
      Naftiko Signals is an investment-and-technology intelligence layer that
      tracks how companies invest in technology categories — including APIs —
      across industries. As reported on signals.naftiko.io, the platform
      currently indexes 884 companies across 50 industries and 44 signal
      groups, harvesting public signals (job postings, GitHub, blogs,
      changelogs) and emitting JSON-LD-described company records so agents and
      analysts can reason about API providers in context. It complements
      OpenAPI-centric catalogs like APIs.guru by capturing the people,
      hiring, and organizational signals around an API.
    humanURL: https://signals.naftiko.io
    tags:
      - Signals
      - Intelligence
      - Companies
      - JSON-LD
    properties:
      - type: Portal
        url: https://signals.naftiko.io
      - type: GitHubOrganization
        url: https://github.com/naftiko
      - type: GitHubRepository
        url: https://github.com/api-evangelist/naftiko

  - 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, Naftiko Signals) 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 Naftiko Signals company
          records 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.
      - name: Naftiko Signals + JSON-LD
        description: >-
          Naftiko Signals publishes company records as JSON-LD so that they
          can be joined to schema.org/Organization in downstream agents.

  - 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.
      - name: Signals-Based Intelligence
        description: >-
          Naftiko Signals layers people-and-investment intelligence on top
          of the spec-driven knowledge layer.

maintainers:
  - FN: Kin Lane
    email: [email protected]
    url: http://kinlane.com