desktop-touch-mcp

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browser_eval

Evaluate JavaScript, extract DOM HTML, or read SSR-injected SPA state to inspect and operate on browser tabs via CDP.

Instructions

Purpose: Inspect or operate on a browser tab via 3 actions: 'js' (evaluate JS), 'dom' (get HTML), 'appState' (extract SSR-injected SPA state). Details: action='js' — Run a JS expression. withPerception:true wraps in {ok, result, post}. action='dom' — Return outerHTML of selector (or document.body), truncated to maxLength. action='appState' — Scan Next/Nuxt/Remix/Apollo/GitHub/Redux SSR injected JSON; pass selectors to override defaults. Prefer: Use action='appState' BEFORE 'dom' or 'js' on SPAs where rendered HTML is sparse — single CDP call. Use 'dom' when 'appState' is empty and you need page structure. Use 'js' as the escape hatch for arbitrary scripting. Caveats: DOM nodes cannot be returned from action='js' directly (circular refs are serialized safely). React/Vue/Svelte controlled inputs cannot be set via element.value — use keyboard(action='type') / browser_fill instead. readyState is strictly checked; guard blocks if page is still loading. Typed errors: code:'BrowserNotConnected' on CDP disconnect (re-attach via browser_open); code:'AutoGuardBlocked' when the auto-guard refuses (e.g. page still loading) — the error message preserves the guard's 1-sentence recommended next step (most often wait_until({condition:'ready_state'}) or browser_eval readyState polling, then retry). Examples: browser_eval({action:'js', expression:'document.title'}) → page title browser_eval({action:'dom', selector:'#main', maxLength:5000}) → outerHTML browser_eval({action:'appState'}) → default SPA state probes

Input Schema

TableJSON Schema

Name	Required	Description
`port`	No	Chrome/Edge CDP remote debugging port (default 9222; configurable via desktop-touch-config.json)
`tabId`	No	Tab ID from browser_open. Omit to use the first page tab.
`action`	Yes	Action selector — one of: js, dom, appState. Per-action required fields are enforced at call time (see the tool description); this flat schema lists every action's fields as optional.
`lensId`	No	Optional perception lens ID. Guards (target.identityStable) are evaluated before eval.
`include`	No	Optional response-shape opt-in. `['envelope']` returns the self-documenting envelope (`_version` / `data` / `as_of` / `confidence`). `['raw']` forces raw shape (overrides DESKTOP_TOUCH_ENVELOPE=1 server default). Default behaviour is raw shape (compat with existing clients).
`maxBytes`	No	Max bytes per individual payload (default 4000). Larger payloads are truncated.
`selector`	No	CSS selector for root element. Omit for document.body.
`maxLength`	No	Max characters of HTML to return (default 10000).
`selectors`	No	Custom probe selectors. Omit to use the default SPA framework set (__NEXT_DATA__ / __NUXT_DATA__ / __REMIX_CONTEXT__ / __APOLLO_STATE__ / window:__INITIAL_STATE__ etc.). Window globals must be prefixed with 'window:'.
`expression`	No	JavaScript expression to evaluate. The server automatically wraps snippets in an async IIFE to avoid repeated const/let collisions. For multi-statement snippets, use an explicit final return value. Declarations (const/let/var) are scoped per snippet — use window.* / globalThis.* for persistence. A single eval is bounded by the CDP per-command timeout (~15s): do NOT write in-page polling loops here — use wait_until (element_matches / url_matches / ready_state) to wait for conditions instead.
`includeContext`	No	When true (default), append `activeTab` + `readyState` lines to the response. Set false to skip — saves ~150 tokens per call when chaining several browser_* calls in the same tab.
`withPerception`	No	When true, return structured JSON {ok, result, post} with post.perception attached. Default false preserves raw-text return.

Schema Changelog

Changes observed during successful MCP inspections.

Changed5 schema fields changedv2.3.1Oct 13, 2026

addedInput schema / $schema

Added value: +"http://json-schema.org/draft-07/schema#"

removedInput schema / additionalProperties
```
Removed value: -false
```

changedInput schema / properties / includeContext / description

Previous value: -"When true, append activeTab and readyState context to the response."New value: +"When true (default), append `activeTab` + `readyState` lines to the response. Set false to skip — saves ~150 tokens per call when chaining several browser_* calls in the same tab."

changedInput schema / properties / port / description

Previous value: -"Chrome/Edge CDP remote debugging port."New value: +"Chrome/Edge CDP remote debugging port (default 9222; configurable via desktop-touch-config.json)"

addedInput schema / properties / selectors / items
```
Added value: +{
+  "type": "string"
+}
```

Addedv1.12.0Jul 8, 2026
Removedv1.10.4Jun 16, 2026
Addedv1.9.2May 25, 2026
Removedv1.8.0May 23, 2026
Addedv1.6.0May 16, 2026
Removedv1.5.1May 12, 2026
Addedv1.5.0May 12, 2026
Removedv1.4.3May 11, 2026
Addedv1.4.2May 10, 2026
Removedv1.4.0May 9, 2026

Changed1 schema field changedv1.2.1May 3, 2026

changedInput schema / oneOf

Previous value: -[
-  {
-    "additionalProperties": false,
-    "properties": {
-      "action": {
-        "const": "js"
-      },
-      "expression": {
-        "description": "JavaScript expression to evaluate. The server automatically wraps snippets in an async IIFE to avoid repeated const/let collisions. For multi-statement snippets, use an explicit final return value. Declarations (const/let/var) are scoped per snippet — use window.* / globalThis.* for persistence.",
-        "type": "string"
-      },
-      "includeContext": {
-        "default": true,
-        "description": "When true, append activeTab and readyState context to the response.",
-        "type": "boolean"
-      },
-      "lensId": {
-        "description": "Optional perception lens ID. Guards (target.identityStable) are evaluated before eval.",
-        "type": "string"
-      },
-      "port": {
-        "default": 9222,
-        "description": "Chrome/Edge CDP remote debugging port.",
-        "maximum": 65535,
-        "minimum": 1,
-        "type": "integer"
-      },
-      "tabId": {
-        "description": "Tab ID from browser_open. Omit to use the first page tab.",
-        "type": "string"
-      },
-      "withPerception": {
-        "default": false,
-        "description": "When true, return structured JSON {ok, result, post} with post.perception attached. Default false preserves raw-text return.",
-        "type": "boolean"
-      }
-    },
-    "required": [
-      "action",
-      "expression"
-    ],
-    "type": "object"
-  },
-  {
-    "additionalProperties": false,
-    "properties": {
-      "action": {
-        "const": "dom"
-      },
-      "includeContext": {
-        "default": true,
-        "description": "When true, append activeTab and readyState context to the response.",
-        "type": "boolean"
-      },
-      "maxLength": {
-        "default": 10000,
-        "description": "Max characters of HTML to return (default 10000).",
-        "maximum": 100000,
-        "minimum": 100,
-        "type": "integer"
-      },
-      "port": {
-        "default": 9222,
-        "description": "Chrome/Edge CDP remote debugging port.",
-        "maximum": 65535,
-        "minimum": 1,
-        "type": "integer"
-      },
-      "selector": {
-        "description": "CSS selector for root element. Omit for document.body.",
-        "type": "string"
-      },
-      "tabId": {
-        "description": "Tab ID from browser_open. Omit to use the first page tab.",
-        "type": "string"
-      }
-    },
-    "required": [
-      "action"
-    ],
-    "type": "object"
-  },
-  {
-    "additionalProperties": false,
-    "properties": {
-      "action": {
-        "const": "appState"
-      },
-      "includeContext": {
-        "default": true,
-        "description": "When true, append activeTab and readyState context to the response.",
-        "type": "boolean"
-      },
-      "maxBytes": {
-        "default": 4000,
-        "description": "Max bytes per individual payload (default 4000). Larger payloads are truncated.",
-        "maximum": 64000,
-        "minimum": 256,
-        "type": "integer"
-      },
-      "port": {
-        "default": 9222,
-        "description": "Chrome/Edge CDP remote debugging port.",
-        "maximum": 65535,
-        "minimum": 1,
-        "type": "integer"
-      },
-      "selectors": {
-        "description": "Custom probe selectors. Omit to use the default SPA framework set (__NEXT_DATA__ / __NUXT_DATA__ / __REMIX_CONTEXT__ / __APOLLO_STATE__ / window:__INITIAL_STATE__ etc.). Window globals must be prefixed with 'window:'.",
-        "type": "array"
-      },
-      "tabId": {
-        "description": "Tab ID from browser_open. Omit to use the first page tab.",
-        "type": "string"
-      }
-    },
-    "required": [
-      "action"
-    ],
-    "type": "object"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "properties": {
+      "action": {
+        "const": "js"
+      },
+      "expression": {
+        "description": "JavaScript expression to evaluate. The server automatically wraps snippets in an async IIFE to avoid repeated const/let collisions. For multi-statement snippets, use an explicit final return value. Declarations (const/let/var) are scoped per snippet — use window.* / globalThis.* for persistence.",
+        "type": "string"
+      },
+      "include": {
+        "description": "Optional response-shape opt-in. `['envelope']` returns the self-documenting envelope (`_version` / `data` / `as_of` / `confidence`). `['raw']` forces raw shape (overrides DESKTOP_TOUCH_ENVELOPE=1 server default). Default behaviour is raw shape (compat with existing clients).",
+        "items": {
+          "type": "string"
+        },
+        "type": "array"
+      },
+      "includeContext": {
+        "default": true,
+        "description": "When true, append activeTab and readyState context to the response.",
+        "type": "boolean"
+      },
+      "lensId": {
+        "description": "Optional perception lens ID. Guards (target.identityStable) are evaluated before eval.",
+        "type": "string"
+      },
+      "port": {
+        "default": 9222,
+        "description": "Chrome/Edge CDP remote debugging port.",
+        "maximum": 65535,
+        "minimum": 1,
+        "type": "integer"
+      },
+      "tabId": {
+        "description": "Tab ID from browser_open. Omit to use the first page tab.",
+        "type": "string"
+      },
+      "withPerception": {
+        "default": false,
+        "description": "When true, return structured JSON {ok, result, post} with post.perception attached. Default false preserves raw-text return.",
+        "type": "boolean"
+      }
+    },
+    "required": [
+      "action",
+      "expression"
+    ],
+    "type": "object"
+  },
+  {
+    "additionalProperties": false,
+    "properties": {
+      "action": {
+        "const": "dom"
+      },
+      "include": {
+        "description": "Optional response-shape opt-in. `['envelope']` returns the self-documenting envelope (`_version` / `data` / `as_of` / `confidence`). `['raw']` forces raw shape (overrides DESKTOP_TOUCH_ENVELOPE=1 server default). Default behaviour is raw shape (compat with existing clients).",
+        "items": {
+          "type": "string"
+        },
+        "type": "array"
+      },
+      "includeContext": {
+        "default": true,
+        "description": "When true, append activeTab and readyState context to the response.",
+        "type": "boolean"
+      },
+      "maxLength": {
+        "default": 10000,
+        "description": "Max characters of HTML to return (default 10000).",
+        "maximum": 100000,
+        "minimum": 100,
+        "type": "integer"
+      },
+      "port": {
+        "default": 9222,
+        "description": "Chrome/Edge CDP remote debugging port.",
+        "maximum": 65535,
+        "minimum": 1,
+        "type": "integer"
+      },
+      "selector": {
+        "description": "CSS selector for root element. Omit for document.body.",
+        "type": "string"
+      },
+      "tabId": {
+        "description": "Tab ID from browser_open. Omit to use the first page tab.",
+        "type": "string"
+      }
+    },
+    "required": [
+      "action"
+    ],
+    "type": "object"
+  },
+  {
+    "additionalProperties": false,
+    "properties": {
+      "action": {
+        "const": "appState"
+      },
+      "include": {
+        "description": "Optional response-shape opt-in. `['envelope']` returns the self-documenting envelope (`_version` / `data` / `as_of` / `confidence`). `['raw']` forces raw shape (overrides DESKTOP_TOUCH_ENVELOPE=1 server default). Default behaviour is raw shape (compat with existing clients).",
+        "items": {
+          "type": "string"
+        },
+        "type": "array"
+      },
+      "includeContext": {
+        "default": true,
+        "description": "When true, append activeTab and readyState context to the response.",
+        "type": "boolean"
+      },
+      "maxBytes": {
+        "default": 4000,
+        "description": "Max bytes per individual payload (default 4000). Larger payloads are truncated.",
+        "maximum": 64000,
+        "minimum": 256,
+        "type": "integer"
+      },
+      "port": {
+        "default": 9222,
+        "description": "Chrome/Edge CDP remote debugging port.",
+        "maximum": 65535,
+        "minimum": 1,
+        "type": "integer"
+      },
+      "selectors": {
+        "description": "Custom probe selectors. Omit to use the default SPA framework set (__NEXT_DATA__ / __NUXT_DATA__ / __REMIX_CONTEXT__ / __APOLLO_STATE__ / window:__INITIAL_STATE__ etc.). Window globals must be prefixed with 'window:'.",
+        "type": "array"
+      },
+      "tabId": {
+        "description": "Tab ID from browser_open. Omit to use the first page tab.",
+        "type": "string"
+      }
+    },
+    "required": [
+      "action"
+    ],
+    "type": "object"
+  }
+]

Addedv1.0.3Apr 26, 2026
Removedv0.15.7Apr 20, 2026

Changed1 schema field changedv0.13.1Apr 17, 2026

addedInput schema / properties / withPerception

Added value: +{
+  "default": false,
+  "description": "When true, return structured JSON { ok, result, post } instead of raw text. Enables post.perception attachment so the LLM can see guard status. Default false preserves the raw-text return for backwards compatibility. Example: browser_eval({expression:'document.title', withPerception:true})",
+  "type": "boolean"
+}

Changed9 schema fields changedv0.10.0Apr 16, 2026

removedInput schema / $schema

Removed value: -"http://json-schema.org/draft-07/schema#"

addedInput schema / additionalProperties
```
Added value: +false
```

removedInput schema / properties / _stub

Removed value: -{
-  "description": "Stub tool — arguments ignored."
-}

addedInput schema / properties / expression

Added value: +{
+  "description": "JavaScript expression to evaluate in the browser tab",
+  "type": "string"
+}

addedInput schema / properties / includeContext

Added value: +{
+  "default": true,
+  "description": "When true, append activeTab and readyState context to the response.",
+  "type": "boolean"
+}

addedInput schema / properties / lensId

Added value: +{
+  "description": "Optional perception lens ID. Guards (target.identityStable) are evaluated before eval. Note: browser_eval returns raw text, so no perception envelope is attached (guards only).",
+  "type": "string"
+}

addedInput schema / properties / port

Added value: +{
+  "default": 9222,
+  "description": "Chrome/Edge CDP remote debugging port.",
+  "maximum": 65535,
+  "minimum": 1,
+  "type": "integer"
+}

addedInput schema / properties / tabId

Added value: +{
+  "description": "Tab ID from browser_connect. Omit to use the first page tab.",
+  "type": "string"
+}

addedInput schema / required
```
Added value: +[
+  "expression"
+]
```

First observedv0.6.2Apr 14, 2026

TDQS

A4.7/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden and discharges it: circular-ref serialization, controlled-input restrictions, strict readyState checking, and two typed errors (BrowserNotConnected, AutoGuardBlocked) with their recovery paths. It also notes the ~15s CDP eval bound and that polling loops belong in wait_until.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Labeled sections (Purpose / Details / Prefer / Caveats / Examples) are well front-loaded and skimmable. The Examples block re-states call shapes already implied by the schema, which is mild redundancy, but overall every section contributes.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 12-parameter, no-annotation, no-output-schema tool this covers actions, error taxonomy, alternatives, and caveats thoroughly. The one gap is that return shapes per action are shown only by example rather than described, though withPerception and includeContext hints partially bridge it.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3, but the description adds real value: it ties parameters to actions (selector/maxLength belong to 'dom', selectors to 'appState'), explains withPerception's {ok, result, post} wrapping, and notes that per-action required fields are enforced at call time despite the flat schema. That last point is a genuine clarification of a schema quirk.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Inspect or operate on a browser tab') and immediately enumerates the three actions (js/dom/appState) with a one-line gloss of each. This distinguishes it from siblings like browser_navigate, browser_click, and browser_locate without opening a schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The 'Prefer' block gives explicit routing rules: appState before dom/js on SPAs, dom when appState is empty, js as the escape hatch, and keyboard/browser_fill instead of value-setting on controlled inputs. Alternatives and exclusions are stated, not implied.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

browser_eval

Instructions

Input Schema

Schema Changelog

TDQS

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