Documentation
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Overview ¶
Package uispec defines constants and _meta types for the MCP Apps extension (io.modelcontextprotocol/ui), spec version 2026-01-26.
It is deliberately free of any MCP SDK dependency: everything is expressed as plain Go types and map[string]any meta maps, so gomukit widgets can be wired into any Go MCP implementation. The official go-sdk adapter lives in package gosdk.
Spec names that may still shift with upcoming spec revisions (the meta key, notification method names) are encoded here exactly once; the TypeScript runtime mirrors them from ui/src/spec-constants.json, and tests cross-check the two.
Index ¶
Constants ¶
const ( // ExtensionID is the MCP Apps extension identifier used in capability // negotiation. ExtensionID = "io.modelcontextprotocol/ui" // SpecVersion is the ext-apps specification version gomukit targets. SpecVersion = "2026-01-26" // MIMEType is the media type of MCP Apps HTML template resources. MIMEType = "text/html;profile=mcp-app" // MetaKey is the key under which UI metadata is nested inside _meta on // tools, resources, and tool results. MetaKey = "ui" // URIScheme is the URI scheme for UI template resources ("ui://..."). URIScheme = "ui" )
const ( VisibilityModel = "model" // tool is callable by the model VisibilityApp = "app" // tool is callable from the app UI only )
Visibility values for ToolUIMeta.Visibility.
Variables ¶
var Grant = &Permission{}
Grant is the marker used to request a permission, e.g. Permissions{Camera: uispec.Grant}.
Functions ¶
func MergeMeta ¶
MergeMeta merges src into dst recursively (map values merge, everything else overwrites) and returns dst. A nil dst is allocated. src is not modified; nested maps from src are copied on merge conflicts only — callers must not retain and mutate src maps that end up shared in dst.
func ValidateURI ¶
ValidateURI checks that uri is a well-formed ui:// resource URI.
Types ¶
type CSP ¶
type CSP struct {
ConnectDomains []string `json:"connectDomains,omitempty"`
ResourceDomains []string `json:"resourceDomains,omitempty"`
FrameDomains []string `json:"frameDomains,omitempty"`
BaseURIDomains []string `json:"baseUriDomains,omitempty"`
}
CSP declares the external origins a UI resource needs. Hosts apply a fully locked-down policy by default; every domain must be predeclared.
type Permission ¶
type Permission struct{}
Permission is the presence marker for a requested sandbox permission. Per the MCP Apps spec each requested capability is a key mapping to an empty object, so a *Permission serializes to {} when set and is omitted when nil.
type Permissions ¶
type Permissions struct {
Camera *Permission `json:"camera,omitempty"`
Microphone *Permission `json:"microphone,omitempty"`
Geolocation *Permission `json:"geolocation,omitempty"`
ClipboardWrite *Permission `json:"clipboardWrite,omitempty"`
}
Permissions declares the browser capabilities a UI resource requests. Hosts MAY honor these by setting the sandbox iframe's allow attribute; apps must not assume they are granted. Serializes to the spec object shape, e.g. {"camera":{},"clipboardWrite":{}}.
type ResourceDescriptor ¶
type ResourceDescriptor struct {
URI string
Name string
Title string
Description string
MIMEType string // always MIMEType for gomukit widgets
UI *ResourceUIMeta
}
ResourceDescriptor carries everything needed to register a widget's template resource with an MCP server, independent of the SDK in use.
func (ResourceDescriptor) MetaMap ¶
func (d ResourceDescriptor) MetaMap() map[string]any
MetaMap returns the descriptor's resource _meta map, or nil when the descriptor declares no UI metadata.
type ResourceUIMeta ¶
type ResourceUIMeta struct {
CSP *CSP `json:"csp,omitempty"`
Permissions *Permissions `json:"permissions,omitempty"`
Domain string `json:"domain,omitempty"`
PrefersBorder *bool `json:"prefersBorder,omitempty"`
}
ResourceUIMeta is the _meta.ui payload attached to a ui:// resource.
func (ResourceUIMeta) MetaMap ¶
func (m ResourceUIMeta) MetaMap() map[string]any
MetaMap returns the resource _meta map: {"ui": {...}}.
type ToolUIMeta ¶
type ToolUIMeta struct {
ResourceURI string `json:"resourceUri"`
Visibility []string `json:"visibility,omitempty"`
}
ToolUIMeta is the _meta.ui payload attached to a tool, linking it to its UI template resource.
func (ToolUIMeta) MetaMap ¶
func (m ToolUIMeta) MetaMap() map[string]any
MetaMap returns the tool _meta map: {"ui": {"resourceUri": ..., ...}}.
Source Files