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nex-browser

NexBrowser MCP Server

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nex_browser_take_screenshot

Capture browser viewport, target element, or clip screenshots and map image pixels to click coordinates for visual inspection and precise interaction.

Instructions

Capture the viewport, one target, or a viewport clip (target, clip and fullPage=true are mutually exclusive). The returned origin and pixelsPerCssPixel map image pixels to nex_browser_mouse_click_xy coordinates. Page CAPTCHA: start with nex_browser_captcha_prepare (free). Do not solve CAPTCHAs with CDP, Python, image matching or scripted drags.

Input Schema

NameRequiredDescriptionDefault
clipNo
typeNo
scaleNo
pageIdNoDefaults to the active page
targetNoSnapshot ref (e12) or unique CSS selector
qualityNo
filenameNo
fullPageNo
sessionIdNoDefaults to the active session

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed5 schema fields changedv2026.10.24
    • addedInput schema / properties / clip
      Added value: +{
+  "additionalProperties": false,
+  "properties": {
+    "height": {
+      "exclusiveMinimum": 0,
+      "type": "number"
+    },
+    "width": {
+      "exclusiveMinimum": 0,
+      "type": "number"
+    },
+    "x": {
+      "minimum": 0,
+      "type": "number"
+    },
+    "y": {
+      "minimum": 0,
+      "type": "number"
+    }
+  },
+  "required": [
+    "x",
+    "y",
+    "width",
+    "height"
+  ],
+  "type": "object"
+}
    • changedInput schema / properties / pageId / description
      Previous value: -"Stable page ID; defaults to the session active page"New value: +"Defaults to the active page"
    • addedInput schema / properties / scale
      Added value: +{
+  "enum": [
+    "css",
+    "device"
+  ],
+  "type": "string"
+}
    • changedInput schema / properties / sessionId / description
      Previous value: -"Optional session ID; defaults to this MCP client active session"New value: +"Defaults to the active session"
    • addedInput schema / properties / target
      Added value: +{
+  "description": "Snapshot ref (e12) or unique CSS selector",
+  "type": "string"
+}
  2. Addedv2026.8.14

TDQS

A3.8/5.0
Behavior4/5

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

With no annotations, the description carries the burden and does disclose non-obvious behavior: the returned origin and pixelsPerCssPixel map image pixels to nex_browser_mouse_click_xy coordinates, plus a policy constraint forbidding CDP/scripted CAPTCHA solving. It omits permission/auth requirements and whether filename writes to disk.

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?

Three dense sentences with the mutually-exclusive constraint front-loaded and no filler. Parenthetical packing is slightly awkward but every clause adds information.

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

Completeness3/5

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

For a 9-parameter tool with no output schema and low schema coverage, the description should say more about scale, quality, and especially filename behavior (does it persist a file?). Return-value context is partly covered by the origin/pixelsPerCssPixel note, but input-side gaps remain.

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

Parameters3/5

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

Schema coverage is only 33% across 9 params; the description handles clip/target/fullPage semantics and target's snapshot-ref format, but leaves scale, type, quality, filename, pageId and sessionId unexplained. Partial compensation for a low-coverage schema, so the minimum-viable baseline.

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

Purpose4/5

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

States a specific verb (Capture) plus resource (viewport, target, viewport clip), and disambiguates the three capture modes as mutually exclusive. It doesn't explicitly distinguish itself from nex_browser_snapshot, though it references snapshot refs as target values, which implies the relationship.

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

Usage Guidelines4/5

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

Gives real routing guidance: the mutual-exclusivity rule for target/clip/fullPage, and an explicit CAPTCHA instruction pointing to nex_browser_captcha_prepare as the free starting point. No exclusions relative to nex_browser_snapshot or guidance on when a full-page vs clipped capture is preferred, so not a 5.

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

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