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: kinlane@gmail.com url: http://kinlane.com