Spider MCP Server

spider_browser_screenshot

Take a screenshot of the current browser page and receive a base64-encoded PNG image for visual verification, debugging, or capturing page state.

Instructions

Take a screenshot of the current page. Returns a base64-encoded PNG image. Use for visual verification, debugging, or capturing page state.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "session_id": "<session_id>"
    },
    "name": "spider_browser_screenshot"
  }
}

Input Schema

Name	Required	Description	Default
`session_id`	Yes	Session ID from spider_browser_open

Schema Changelog

Changes observed during successful MCP inspections.

First observedv2.1.2Jul 6, 2026

TDQS

A4.3/5.0

Behavior4/5

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

No annotations provided, but description discloses that it returns a base64-encoded PNG, which is sufficient for a read-only screenshot tool. No contradictions.

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

Conciseness5/5

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

Two concise sentences, front-loaded with purpose and output format. No redundant information.

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

Completeness5/5

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

Complete for a simple tool with one parameter and no output schema. Covers purpose, output, and use cases effectively.

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 100% with one parameter (session_id) well-described. Description adds no extra parameter detail beyond the schema, so baseline score of 3 is appropriate.

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?

Description clearly states 'Take a screenshot of the current page' with a specific verb and resource, differentiating from siblings like spider_browser_content or spider_screenshot.

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?

Explicitly mentions use cases: visual verification, debugging, or capturing page state. Could be improved by noting when to avoid (e.g., dynamic content) but still clear.

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