McpProtocol class

MCP protocol versions and constants

Constructors

McpProtocol()

Properties

hashCode → int

The hash code for this object.

no setter, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited

Static Methods

defaultSchemaDialect(String version) → String?

The default JSON Schema dialect a peer should assume for schemas that omit $schema under the negotiated version. 2025-11-25 pins 2020-12 (SEP-1613); earlier revisions left the dialect unspecified (returns null — callers must not stamp a dialect for those peers).

isStateless(String version) → bool

Whether the version uses the stateless core (no handshake/session): client info/caps in _meta per request, server/discover for caps, MCP-Protocol-Version as the sole version signal. Introduced 2026-07-28. See docs/STATELESS-COEXISTENCE-DESIGN.md.

isVersionSupported(String version) → bool

Check if a version is supported

negotiateVersion(List<String> clientVersions, List<String> serverVersions) → String?

Get the best common version from client and server versions

requiresProtocolHeader(String version) → bool

Whether the negotiated version requires the MCP-Protocol-Version HTTP header on every post-handshake request (mandatory from 2025-06-18).

schemaWithDefaultDialect(Map<String, dynamic> schema, String version) → Map<String, dynamic>

Return a copy of schema annotated with the 2020-12 $schema dialect when (a) the negotiated version pins a default dialect and (b) the schema does not already declare its own $schema. Free-form schemas that already carry a $schema — or any schema under an older negotiated revision — are returned unchanged. Non-mutating: the input map is never modified.

supportsBatching(String version) → bool

Whether the negotiated version supports JSON-RPC batching. Removed in 2025-06-18.

supportsElicitation(String version) → bool

Whether the negotiated version understands elicitation/create (introduced 2025-06-18).

supportsIconsAndSamplingTools(String version) → bool

Whether the negotiated version understands icons, sampling tools / toolChoice, URL-mode elicitation, multi-select / default-valued elicitation primitives, and Implementation.description (all introduced in 2025-11-25). Mirrors the server package's McpProtocol.supportsIconsAndSamplingTools predicate so both sides gate the same behavior on the same negotiated revision.

supportsImplementationDescription(String version) → bool

Whether the negotiated version carries Implementation.description on clientInfo / serverInfo (2025-11-25). Older peers ignore an emitted description, so emission is additive; this predicate exists so callers may suppress it for strict older-revision fixtures.

supportsSamplingTools(String version) → bool

Whether the negotiated version understands sampling tool calling — the tools / toolChoice request fields and tool-call results on sampling/createMessage (SEP: sampling with tools, 2025-11-25). Alias of supportsIconsAndSamplingTools scoped to the sampling surface.

supportsUrlElicitation(String version) → bool

Whether the negotiated version understands URL-mode elicitation (mode: "url", SEP-1036), multi-select enums (SEP-1330), and default values in elicitation primitives (SEP-1034). All landed in 2025-11-25.

Constants

defaultVersion → const String

Default protocol version (latest supported).

errorInternal → const int

errorInvalidParams → const int

errorInvalidRequest → const int

errorMethodNotFound → const int

errorParse → const int

Standard error codes

errorPromptNotFound → const int

errorProtocolError → const int

errorResourceAccessDenied → const int

errorResourceNotFound → const int

MCP-specific error codes

errorToolExecutionFailed → const int

errorToolNotFound → const int

jsonRpcVersion → const String

JSON-RPC version

jsonSchemaDialect2020_12 → const String

Canonical JSON Schema dialect for tool inputSchema / outputSchema and elicitation requestedSchema when the negotiated revision is 2025-11-25+ (SEP-1613). A schema that omits $schema is interpreted against this dialect; existing schemas that declare their own $schema are left untouched.

methodAuthorize → const String

Authorization methods (2025-03-26)

methodCallTool → const String

methodCancelled → const String

methodCancelTool → const String

methodCapabilitiesUpdate → const String

2025-03-26 New methods

methodComplete → const String

methodGetPrompt → const String

methodInitialize → const String

Standard MCP methods

methodInitialized → const String

methodListPrompts → const String

methodListResources → const String

methodListResourceTemplates → const String

methodListRoots → const String

methodListTools → const String

methodLog → const String

methodProgress → const String

Notifications

methodPromptListChanged → const String

methodReadResource → const String

methodRefresh → const String

methodResourceListChanged → const String

methodResourceUpdated → const String

methodRevoke → const String

methodRootListChanged → const String

methodSetLevel → const String

methodShutdown → const String

methodSubscribeResource → const String

methodToken → const String

methodToolListChanged → const String

methodUnsubscribeResource → const String

progressTokenNumber → const String

progressTokenString → const String

Progress token types

supportedVersions → const List<String>

Supported protocol versions in order of preference (newest first).

v2024_11_05 → const String

Protocol version 2024-11-05

v2025_03_26 → const String

Protocol version 2025-03-26

v2025_06_18 → const String

Protocol version 2025-06-18 — adds elicitation, structured tool output, resource_link, OAuth Resource Server, MCP-Protocol-Version header. Removes JSON-RPC batching.

v2025_11_25 → const String

Protocol version 2025-11-25 — adds icons, sampling tool calling (tools / toolChoice), URL-mode elicitation, OIDC Discovery, Client ID Metadata Documents, default values in elicitation primitives.

v2026_07_28 → const String

Protocol version 2026-07-28 — BREAKING: stateless core (removes the initialize/initialized handshake and Mcp-Session-Id; client info/caps ride _meta on every request; server/discover fetches caps on demand), Extensions framework, Tasks extension, auth hardening, deprecations (Roots/Sampling/Logging). Adopted as an additive, version-gated parallel path — the handshake path stays for ≤2025-11-25 peers. NOT yet in supportedVersions until the stateless request path lands (opt-in via a stateless connection mode).