{ "title": "MCP vs A2A Myths and Evidence", "schemaVersion": "1.0", "researchFreeze": "2026-08-26", "protocolRevision": "MCP 2026-07-28 / A2A 1.0", "mcpRevision": "2026-07-28", "a2aCompatibilityLine": "1.0", "a2aWebsiteSpecificationLabel": "1.0.0", "a2aRepositoryPatchTag": "v1.0.1", "a2aVersionSemantics": "A2A negotiates major.minor 1.0; patch tags identify specification releases and are not negotiated.", "count": 35, "records": [ { "id": "R8-MYTH001", "myth": "A2A replaces MCP", "assessment": "False", "correction": "Official A2A materials call them complementary.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH002", "myth": "MCP is agent-to-agent", "assessment": "Usually false", "correction": "MCP primarily connects hosts/agents to capabilities; an implementation may wrap an agent.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH003", "myth": "A2A is just tool calling between agents", "assessment": "False", "correction": "A2A defines Messages, Tasks, Artifacts, Agent Cards, streaming and push delivery.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH004", "myth": "Every MCP server is an agent", "assessment": "False", "correction": "An MCP server may be a deterministic wrapper with no model or autonomy.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH005", "myth": "Every A2A server contains an LLM", "assessment": "Not required", "correction": "The protocol defines an agent role, not a mandatory model implementation.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH006", "myth": "An A2A skill is the same as an MCP tool", "assessment": "False", "correction": "A skill is descriptive and can encompass many internal operations.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH007", "myth": "MCP Tasks and A2A Tasks are compatible", "assessment": "False", "correction": "They have different methods, states, negotiation and semantics.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH008", "myth": "A2A Tasks are optional extensions", "assessment": "False", "correction": "Task is a core A2A object; a direct Message can be returned for simpler work.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH009", "myth": "MCP Tasks are core MCP", "assessment": "False in current MCP", "correction": "Current Tasks are an extension.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH010", "myth": "A2A only uses JSON-RPC", "assessment": "False in v1.0", "correction": "JSON-RPC, HTTP+JSON/REST and gRPC are core bindings.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH011", "myth": "MCP only uses HTTP", "assessment": "False", "correction": "stdio remains a core transport.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH012", "myth": "Both protocols require persistent sessions", "assessment": "False", "correction": "Current MCP is sessionless; A2A uses explicit Task/context state over stateless infrastructure.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH013", "myth": "Agent Cards prove an agent is safe", "assessment": "False", "correction": "Signatures can establish integrity/origin, not behavioral safety.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH014", "myth": "server/discover is an Agent Card", "assessment": "False", "correction": "It is live MCP capability/version discovery, not an agent identity/skill document.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH015", "myth": "A signed Agent Card proves every skill works", "assessment": "False", "correction": "It proves the signed metadata was not altered and came from the signing identity.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH016", "myth": "A2A hides all agent outputs", "assessment": "False", "correction": "It hides internals while exchanging Messages, status, history and Artifacts.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH017", "myth": "A2A requires agents to reveal chain of thought", "assessment": "False", "correction": "Opaque execution is a guiding principle.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH018", "myth": "Using both protocols automatically preserves user identity", "assessment": "False", "correction": "Bridges must explicitly preserve or exchange identity and authorization context.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH019", "myth": "OAuth makes combined systems secure", "assessment": "False", "correction": "Authorization design, task ownership, content trust and implementation security still matter.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH020", "myth": "A2A is a Google-only protocol", "assessment": "Outdated", "correction": "Google created it, then donated it; it now has multi-company governance and AAIF hosting.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH021", "myth": "MCP is controlled only by Anthropic", "assessment": "Outdated", "correction": "MCP has public governance and AAIF hosting, though its origins remain Anthropic.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH022", "myth": "Both projects share one technical steering committee", "assessment": "False", "correction": "They share an AAIF umbrella but retain distinct technical governance.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH023", "myth": "A2A v1.0 was released in 2025", "assessment": "False", "correction": "The first stable v1.0 release shipped in March 2026.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH024", "myth": "A2A v0.3 and v1.0 are automatically wire-identical", "assessment": "False", "correction": "v1.0 includes breaking changes; compatibility layers are explicit.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH025", "myth": "A2A is a subagent protocol", "assessment": "Officially no", "correction": "The project says it is not a protocol for an agent’s private subagents or tools.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH026", "myth": "A2A replaces APIs", "assessment": "False", "correction": "A2A uses web bindings and agents still call APIs internally.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH027", "myth": "MCP replaces APIs", "assessment": "False", "correction": "MCP servers frequently wrap APIs, databases and SDKs.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH028", "myth": "The vertical/horizontal metaphor fully explains the protocols", "assessment": "Incomplete", "correction": "It obscures task semantics, identity, discovery, local execution and ambiguous boundaries.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH029", "myth": "One gateway can treat all MCP and A2A traffic identically", "assessment": "Unsafe simplification", "correction": "The protocols expose different identities, operations, state and policy units.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH030", "myth": "A2A Artifacts are MCP resources", "assessment": "False", "correction": "They can be bridged conceptually but are different protocol objects.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH031", "myth": "MCP resources are A2A messages", "assessment": "False", "correction": "Resources are URI-addressable server data; Messages are communication turns.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH032", "myth": "A2A remote agents cannot use MCP", "assessment": "False", "correction": "Official architecture explicitly expects many agents to use MCP internally.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH033", "myth": "An MCP server cannot call A2A", "assessment": "False at implementation layer", "correction": "A server can delegate internally, though that composition is outside MCP core semantics.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH034", "myth": "Using A2A always means less control", "assessment": "Too broad", "correction": "Clients can apply policy, but the remote agent intentionally owns more execution discretion.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" }, { "id": "R8-MYTH035", "myth": "Using MCP always means deterministic behavior", "assessment": "False", "correction": "Tools can wrap models, workflows or stochastic services.", "packageSourceIds": [ "S003", "S004", "S038" ], "sourceIds": [ "S339", "S340", "S054" ], "sourceMappingStatus": "editorially-mapped-to-package-evidence" } ] }