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Merge pull request #422 from jonathanhefner/everything-is-external

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Replace "external" with "network" in CSP documentation
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Jonathan Hefner 2026-02-03 10:29:52 -06:00 • committed by GitHub
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6 changed files with 21 additions and 23 deletions
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2
docs/overview.md
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@ -201,7 +201,7 @@ See the [Display Modes](https://github.com/modelcontextprotocol/ext-apps/blob/ma
All Views run in sandboxed iframes with no access to the Host's DOM, cookies, or storage. Communication happens only through [`postMessage`](https://developer.mozilla.org/en-US/docs/Web/API/Window/postMessage), making it auditable. All Views run in sandboxed iframes with no access to the Host's DOM, cookies, or storage. Communication happens only through [`postMessage`](https://developer.mozilla.org/en-US/docs/Web/API/Window/postMessage), making it auditable.
Servers declare which external domains their UI needs via [CSP](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CSP) metadata. Hosts enforce these declarations — if no domains are declared, no external connections are allowed. This "restrictive by default" approach prevents data exfiltration to undeclared servers. Servers declare which network domains their UI needs via [CSP](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CSP) metadata. Hosts enforce these declarations — if no domains are declared, no external connections are allowed. This "restrictive by default" approach prevents data exfiltration to undeclared servers.
See the [Security Implications](https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/2026-01-26/apps.mdx#security-implications) section of the specification for the threat model and mitigations. See the [Security Implications](https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/2026-01-26/apps.mdx#security-implications) section of the specification for the threat model and mitigations.

20
src/generated/schema.json generated
View file

@ -165,14 +165,14 @@
"type": "object", "type": "object",
"properties": { "properties": {
"connectDomains": { "connectDomains": {
"description": "Origins for network requests (fetch/XHR/WebSocket).\n\n- Maps to CSP `connect-src` directive\n- Empty or omitted → no external connections (secure default)", "description": "Origins for network requests (fetch/XHR/WebSocket).\n\n- Maps to CSP `connect-src` directive\n- Empty or omitted → no network connections (secure default)",
"type": "array", "type": "array",
"items": { "items": {
"type": "string" "type": "string"
} }
}, },
"resourceDomains": { "resourceDomains": {
"description": "Origins for static resources (images, scripts, stylesheets, fonts, media).\n\n- Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives\n- Wildcard subdomains supported: `https://*.example.com`\n- Empty or omitted → no external resources (secure default)", "description": "Origins for static resources (images, scripts, stylesheets, fonts, media).\n\n- Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives\n- Wildcard subdomains supported: `https://*.example.com`\n- Empty or omitted → no network resources (secure default)",
"type": "array", "type": "array",
"items": { "items": {
"type": "string" "type": "string"
@ -2511,14 +2511,14 @@
"type": "object", "type": "object",
"properties": { "properties": {
"connectDomains": { "connectDomains": {
"description": "Origins for network requests (fetch/XHR/WebSocket).\n\n- Maps to CSP `connect-src` directive\n- Empty or omitted → no external connections (secure default)", "description": "Origins for network requests (fetch/XHR/WebSocket).\n\n- Maps to CSP `connect-src` directive\n- Empty or omitted → no network connections (secure default)",
"type": "array", "type": "array",
"items": { "items": {
"type": "string" "type": "string"
} }
}, },
"resourceDomains": { "resourceDomains": {
"description": "Origins for static resources (images, scripts, stylesheets, fonts, media).\n\n- Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives\n- Wildcard subdomains supported: `https://*.example.com`\n- Empty or omitted → no external resources (secure default)", "description": "Origins for static resources (images, scripts, stylesheets, fonts, media).\n\n- Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives\n- Wildcard subdomains supported: `https://*.example.com`\n- Empty or omitted → no network resources (secure default)",
"type": "array", "type": "array",
"items": { "items": {
"type": "string" "type": "string"
@ -3874,14 +3874,14 @@
"type": "object", "type": "object",
"properties": { "properties": {
"connectDomains": { "connectDomains": {
"description": "Origins for network requests (fetch/XHR/WebSocket).\n\n- Maps to CSP `connect-src` directive\n- Empty or omitted → no external connections (secure default)", "description": "Origins for network requests (fetch/XHR/WebSocket).\n\n- Maps to CSP `connect-src` directive\n- Empty or omitted → no network connections (secure default)",
"type": "array", "type": "array",
"items": { "items": {
"type": "string" "type": "string"
} }
}, },
"resourceDomains": { "resourceDomains": {
"description": "Origins for static resources (images, scripts, stylesheets, fonts, media).\n\n- Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives\n- Wildcard subdomains supported: `https://*.example.com`\n- Empty or omitted → no external resources (secure default)", "description": "Origins for static resources (images, scripts, stylesheets, fonts, media).\n\n- Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives\n- Wildcard subdomains supported: `https://*.example.com`\n- Empty or omitted → no network resources (secure default)",
"type": "array", "type": "array",
"items": { "items": {
"type": "string" "type": "string"
@ -3913,14 +3913,14 @@
"type": "object", "type": "object",
"properties": { "properties": {
"connectDomains": { "connectDomains": {
"description": "Origins for network requests (fetch/XHR/WebSocket).\n\n- Maps to CSP `connect-src` directive\n- Empty or omitted → no external connections (secure default)", "description": "Origins for network requests (fetch/XHR/WebSocket).\n\n- Maps to CSP `connect-src` directive\n- Empty or omitted → no network connections (secure default)",
"type": "array", "type": "array",
"items": { "items": {
"type": "string" "type": "string"
} }
}, },
"resourceDomains": { "resourceDomains": {
"description": "Origins for static resources (images, scripts, stylesheets, fonts, media).\n\n- Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives\n- Wildcard subdomains supported: `https://*.example.com`\n- Empty or omitted → no external resources (secure default)", "description": "Origins for static resources (images, scripts, stylesheets, fonts, media).\n\n- Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives\n- Wildcard subdomains supported: `https://*.example.com`\n- Empty or omitted → no network resources (secure default)",
"type": "array", "type": "array",
"items": { "items": {
"type": "string" "type": "string"
@ -4082,14 +4082,14 @@
"type": "object", "type": "object",
"properties": { "properties": {
"connectDomains": { "connectDomains": {
"description": "Origins for network requests (fetch/XHR/WebSocket).\n\n- Maps to CSP `connect-src` directive\n- Empty or omitted → no external connections (secure default)", "description": "Origins for network requests (fetch/XHR/WebSocket).\n\n- Maps to CSP `connect-src` directive\n- Empty or omitted → no network connections (secure default)",
"type": "array", "type": "array",
"items": { "items": {
"type": "string" "type": "string"
} }
}, },
"resourceDomains": { "resourceDomains": {
"description": "Origins for static resources (images, scripts, stylesheets, fonts, media).\n\n- Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives\n- Wildcard subdomains supported: `https://*.example.com`\n- Empty or omitted → no external resources (secure default)", "description": "Origins for static resources (images, scripts, stylesheets, fonts, media).\n\n- Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives\n- Wildcard subdomains supported: `https://*.example.com`\n- Empty or omitted → no network resources (secure default)",
"type": "array", "type": "array",
"items": { "items": {
"type": "string" "type": "string"

11
src/generated/schema.ts generated
View file

@ -188,8 +188,7 @@ export const McpUiSandboxProxyReadyNotificationSchema = z.object({
/** /**
* @description Content Security Policy configuration for UI resources. * @description Content Security Policy configuration for UI resources.
* *
* Servers declare which external origins their UI needs to access. * Servers declare which origins their UI requires. Hosts use this to enforce appropriate CSP headers.
* Hosts use this to enforce appropriate CSP headers.
* *
* > [!IMPORTANT] * > [!IMPORTANT]
* > MCP App HTML runs in a sandboxed iframe with no same-origin server. * > MCP App HTML runs in a sandboxed iframe with no same-origin server.
@ -201,7 +200,7 @@ export const McpUiResourceCspSchema = z.object({
* @description Origins for network requests (fetch/XHR/WebSocket). * @description Origins for network requests (fetch/XHR/WebSocket).
* *
* - Maps to CSP `connect-src` directive * - Maps to CSP `connect-src` directive
* - Empty or omitted → no external connections (secure default) * - Empty or omitted → no network connections (secure default)
* *
* @example * @example
* ```ts * ```ts
@ -212,14 +211,14 @@ export const McpUiResourceCspSchema = z.object({
.array(z.string()) .array(z.string())
.optional() .optional()
.describe( .describe(
"Origins for network requests (fetch/XHR/WebSocket).\n\n- Maps to CSP `connect-src` directive\n- Empty or omitted \u2192 no external connections (secure default)", "Origins for network requests (fetch/XHR/WebSocket).\n\n- Maps to CSP `connect-src` directive\n- Empty or omitted \u2192 no network connections (secure default)",
), ),
/** /**
* @description Origins for static resources (images, scripts, stylesheets, fonts, media). * @description Origins for static resources (images, scripts, stylesheets, fonts, media).
* *
* - Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives * - Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives
* - Wildcard subdomains supported: `https://*.example.com` * - Wildcard subdomains supported: `https://*.example.com`
* - Empty or omitted → no external resources (secure default) * - Empty or omitted → no network resources (secure default)
* *
* @example * @example
* ```ts * ```ts
@ -230,7 +229,7 @@ export const McpUiResourceCspSchema = z.object({
.array(z.string()) .array(z.string())
.optional() .optional()
.describe( .describe(
"Origins for static resources (images, scripts, stylesheets, fonts, media).\n\n- Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives\n- Wildcard subdomains supported: `https://*.example.com`\n- Empty or omitted \u2192 no external resources (secure default)", "Origins for static resources (images, scripts, stylesheets, fonts, media).\n\n- Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives\n- Wildcard subdomains supported: `https://*.example.com`\n- Empty or omitted \u2192 no network resources (secure default)",
), ),
/** /**
* @description Origins for nested iframes. * @description Origins for nested iframes.

2
src/server/index.examples.ts
View file

@ -164,7 +164,7 @@ function registerAppResource_basicUsage(server: McpServer) {
} }
/** /**
* Example: registerAppResource with CSP configuration for external domains. * Example: registerAppResource with CSP configuration for network access.
*/ */
function registerAppResource_withCsp( function registerAppResource_withCsp(
server: McpServer, server: McpServer,

2
src/server/index.ts
View file

@ -270,7 +270,7 @@ export function registerAppTool<
* ); * );
* ``` * ```
* *
* @example With CSP configuration for external domains * @example With CSP configuration for network access
* ```ts source="./index.examples.ts#registerAppResource_withCsp" * ```ts source="./index.examples.ts#registerAppResource_withCsp"
* registerAppResource( * registerAppResource(
* server, * server,

7
src/spec.types.ts
View file

@ -539,8 +539,7 @@ export interface McpUiInitializedNotification {
/** /**
* @description Content Security Policy configuration for UI resources. * @description Content Security Policy configuration for UI resources.
* *
* Servers declare which external origins their UI needs to access. * Servers declare which origins their UI requires. Hosts use this to enforce appropriate CSP headers.
* Hosts use this to enforce appropriate CSP headers.
* *
* > [!IMPORTANT] * > [!IMPORTANT]
* > MCP App HTML runs in a sandboxed iframe with no same-origin server. * > MCP App HTML runs in a sandboxed iframe with no same-origin server.
@ -552,7 +551,7 @@ export interface McpUiResourceCsp {
* @description Origins for network requests (fetch/XHR/WebSocket). * @description Origins for network requests (fetch/XHR/WebSocket).
* *
* - Maps to CSP `connect-src` directive * - Maps to CSP `connect-src` directive
* - Empty or omitted → no external connections (secure default) * - Empty or omitted → no network connections (secure default)
* *
* @example * @example
* ```ts * ```ts
@ -565,7 +564,7 @@ export interface McpUiResourceCsp {
* *
* - Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives * - Maps to CSP `img-src`, `script-src`, `style-src`, `font-src`, `media-src` directives
* - Wildcard subdomains supported: `https://*.example.com` * - Wildcard subdomains supported: `https://*.example.com`
* - Empty or omitted → no external resources (secure default) * - Empty or omitted → no network resources (secure default)
* *
* @example * @example
* ```ts * ```ts