# Agent protocols > links + original short summaries; content belongs to publishers 23 entries. JSON: https://agentpaywire.com/api/library/agent-protocols.json Markdown: https://agentpaywire.com/library/agent-protocols.md JSONL: https://agentpaywire.com/library.jsonl Feed: https://agentpaywire.com/library/feed.json Schema: https://agentpaywire.com/schemas/library.schema.json ### 2026-10-06 - [SEP-2127: MCP Server Cards - HTTP Server Discovery](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2127) - id: mcp-sep-2127-server-cards - publisher: GitHub (Model Context Protocol) - date_published: 2026-10-06 - type: spec - tags: mcp, interop, standards - summary: Merged MCP enhancement proposal for pre-connection discovery of remote MCP servers through Server Cards, advertised from a domain-level /.well-known/ai-catalog.json. It supersedes the earlier SEP-1649 approach. The server-card schema is still marked experimental. ### 2026-07-28 - [Specification - Model Context Protocol (Version 2026-07-28)](https://modelcontextprotocol.io/specification/2026-07-28) - id: mcp-specification-2026-07-28 - publisher: Model Context Protocol - date_published: 2026-07-28 - type: spec - tags: mcp, interop, tools - summary: Latest dated version of the Model Context Protocol specification, covering architecture, base protocol, lifecycle, transports, authorization and client and server features. The version identifier is the date. ### 2026-05-27 - [DNS for AI Discovery (draft-mozleywilliams-dnsop-dnsaid-02)](https://datatracker.ietf.org/doc/draft-mozleywilliams-dnsop-dnsaid/) - id: ietf-dns-aid - publisher: IETF Datatracker - authors: Jim Mozley, Nic Williams, Behcet Sarikaya, Roland Schott, Jeffrey Damick - date_published: 2026-05-27 - type: spec - tags: interop, identity, standards - summary: Internet-Draft for publishing AI agent endpoints and capability metadata in DNS using SVCB records and DNS-SD-style indexes, with DNSSEC/DANE for validation. Active individual draft, revision 02. ### 2026-04-17 - [Introducing the Agent Readiness score. Check to see if your site is agent-ready](https://blog.cloudflare.com/agent-readiness) - id: cloudflare-agent-readiness - publisher: Cloudflare Blog - date_published: 2026-04-17 - type: announcement - tags: interop, web-agents, standards - summary: Cloudflare post introducing an Agent Readiness score and the isitagentready.com scanner, which checks emerging standards such as llms.txt, Markdown negotiation, Content Signals, RFC 9727 API catalogs, MCP Server Cards, A2A Agent Cards, Agent Skills and the x402/MPP commerce protocols. ### 2025-06-18 - [Specification - Model Context Protocol (Version 2025-06-18)](https://modelcontextprotocol.io/specification/2025-06-18) - id: mcp-specification-2025-06-18 - publisher: Model Context Protocol - date_published: 2025-06-18 - type: spec - tags: mcp, interop, tools - summary: Earlier dated revision of the MCP specification, covering authorization, transports, roots, sampling, elicitation, prompts and resources. ### 2024-09-03 - [The /llms.txt file, v2](https://llmstxt.org/) - id: llms-txt - publisher: llmstxt.org - authors: Jeremy Howard - date_published: 2024-09-03 - type: spec - tags: llms-txt, interop - summary: Proposal to standardise an /llms.txt file that gives agents information about how to use a website. The page was last modified on 10 August 2026. ### 2021-02-15 - [OpenAPI Specification v3.1.0](https://spec.openapis.org/oas/v3.1.0.html) - id: openapi-3-1-0 - publisher: OpenAPI Initiative - date_published: 2021-02-15 - type: spec - tags: openapi, interop - summary: Standard, programming-language-agnostic interface description for HTTP APIs, widely used to describe tools and APIs for programmatic consumers. ### Undated - [Agent2Agent (A2A) Protocol Specification](https://a2a-protocol.org/latest/specification/) - id: a2a-protocol-specification - publisher: A2A Protocol - date_published: null - type: spec - tags: a2a, interop - summary: Official A2A specification (latest released version 1.0.0), an open standard for communication and interoperability between independent, potentially opaque AI agent systems built on different frameworks or by different vendors. - [RFC 9421: HTTP Message Signatures](https://datatracker.ietf.org/doc/html/rfc9421) - id: rfc-9421-http-message-signatures - publisher: IETF - authors: A. Backman, J. Richer, M. Sporny - date_published: null - type: spec - tags: identity, security, http - summary: IETF Proposed Standard defining how to create, encode and verify digital signatures over components of HTTP messages. It can serve as a building block for authenticating automated clients. Published February 2024 (no day given, so date_published is null). - [Official MCP Registry](https://registry.modelcontextprotocol.io/) - id: mcp-registry - publisher: Model Context Protocol - date_published: null - type: directory - tags: mcp, directory, interop - summary: Official registry of MCP servers with an unauthenticated read API (GET /v0.1/servers) supporting cursor pagination, name search and updated_since for incremental sync by downstream aggregators. - [modelcontextprotocol/registry](https://github.com/modelcontextprotocol/registry) - id: mcp-registry-github - publisher: GitHub (Model Context Protocol) - date_published: null - type: repo - tags: mcp, directory, tools - summary: Source, OpenAPI reference and server.json schema for the community-driven MCP Registry, including the publishing flow and namespace verification. - [modelcontextprotocol/ext-server-card](https://github.com/modelcontextprotocol/experimental-ext-server-card) - id: mcp-ext-server-card - publisher: GitHub (Model Context Protocol) - date_published: null - type: repo - tags: mcp, interop - summary: Experimental extension that holds the TypeScript and JSON Schema source for MCP Server Cards. A card describes a remote server's identity and transport endpoints; tools are listed at runtime, not on the card. - [AI Catalog](https://ai-catalog.io/) - id: ai-catalog - publisher: AI Catalog (Agent-Card) - date_published: null - type: spec - tags: interop, mcp, a2a, standards - summary: Cross-protocol draft standard for a typed, nestable JSON catalog that lists heterogeneous AI artifacts (MCP servers, A2A agents, datasets and more) for discovery. It is developed by members of several AI protocol communities. - [Agent Discovery (A2A Protocol)](https://a2a-protocol.org/latest/topics/agent-discovery/) - id: a2a-agent-discovery - publisher: A2A Protocol - date_published: null - type: docs - tags: a2a, interop - summary: A2A guidance on finding agents through a well-known Agent Card URL (/.well-known/agent-card.json), curated registries, or direct configuration. It notes that the spec does not prescribe a registry API. - [Global A2A Registry](https://www.a2a-registry.org/) - id: a2a-registry-org - publisher: A2A Registry - date_published: null - type: directory - tags: a2a, directory, identity - summary: Free public registry of A2A agents that is itself discoverable as an A2A agent. It offers natural-language agent search and DNS- and GitHub-based verification, and its agent card includes an extension that declares a payment model. - [wild-card-ai/agents-json](https://github.com/wild-card-ai/agents-json) - id: wildcard-agents-json - publisher: GitHub (Wildcard) - date_published: null - type: repo - tags: interop, openapi, tools - summary: agents.json, an OpenAPI-based contract published at /.well-known/agents.json that describes multi-step API 'flows' for agents, linking the outputs of one operation to the inputs of the next. - [Agent Skills](https://agentskills.io/) - id: agentskills-io - publisher: agentskills.io - date_published: null - type: spec - tags: interop, tools, agents - summary: Open format for packaging agent capabilities as SKILL.md files with YAML frontmatter, plus a discovery index schema used by sites at /.well-known/agent-skills/index.json (for example docs.x402.org and mpp.dev). - [AGENTS.md](https://agents.md/) - id: agents-md - publisher: agents.md - date_published: null - type: spec - tags: interop, agents - summary: Simple open format for a README-style instruction file aimed at coding agents. mpp.dev publishes one and links it from its API catalog. - [RFC 9727: api-catalog: A Well-Known URI and Link Relation to Help Discovery of APIs](https://www.rfc-editor.org/rfc/rfc9727) - id: rfc-9727-api-catalog - publisher: IETF - authors: K. Smith - date_published: null - type: spec - tags: openapi, interop, standards, http - summary: Standards-track RFC (June 2025) defining /.well-known/api-catalog and the api-catalog link relation, which return a linkset of a publisher's APIs with links to their descriptions, docs and status endpoints. - [RFC 9728: OAuth 2.0 Protected Resource Metadata](https://www.rfc-editor.org/rfc/rfc9728) - id: rfc-9728-oauth-protected-resource-metadata - publisher: IETF - authors: M.B. Jones, P. Hunt, A. Parecki - date_published: null - type: spec - tags: identity, security, standards, mcp - summary: Standards-track RFC (April 2025) defining metadata that a protected resource publishes so clients can learn how to obtain tokens for it. Remote MCP authorization relies on it. - [Content Signals](https://contentsignals.org/) - id: content-signals - publisher: contentsignals.org - date_published: null - type: spec - tags: web-agents, interop, regulation - summary: robots.txt extension (Content-Signal: search=, ai-input=, ai-train=) that declares how crawled content may be used, settable per user-agent. mpp.dev, x402scan and x402.org use it. - [webmachinelearning/webmcp](https://github.com/webmachinelearning/webmcp) - id: webmcp-github - publisher: GitHub (W3C Web Machine Learning CG) - date_published: null - type: repo - tags: mcp, web-agents, tools - summary: Community Group proposal that lets a web page register tools for in-browser agents (document.modelContext.registerTool with a JSON Schema input). It is a CG draft, not a W3C standard. - [Glama MCP server directory](https://glama.ai/mcp/servers) - id: glama-mcp-servers - publisher: Glama - date_published: null - type: directory - tags: mcp, directory, security - summary: Large MCP server and remote connector directory, described as a superset of the official MCP Registry. Each server is scanned and scored, and the directory has a public REST API with OpenAPI and an RFC 9727 api-catalog.