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neko-browser

neko-browser

by aliksir
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TypeScript
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neko_evaluate

Execute JavaScript in the page context to trigger client-side handlers that clicks cannot activate. Returns evaluation result as JSON.

Instructions

Execute arbitrary JavaScript in the page context (page.evaluate()). Use this when neko_click cannot trigger a client-side handler, such as ASP.NET PostBack (WebForm_DoPostBackWithOptions). Returns the evaluation result as JSON.

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": {
      "expression": "<expression>"
    },
    "name": "neko_evaluate"
  }
}

Input Schema

NameRequiredDescriptionDefault
argNoOptional argument passed to expression (same as Playwright page.evaluate(expr, arg))
expressionYesJavaScript expression or code to execute in the page context

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.1

TDQS

A4.3/5.0
Behavior3/5

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

No annotations provided, so description carries burden. It states the tool executes arbitrary JS and returns JSON, but does not disclose potential side effects or required permissions. For a code execution tool, this is adequate but not thorough.

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 core purpose and usage context. 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?

Given no output schema, it states return type (JSON). Both parameters are fully described in schema. Usage guidance relative to siblings is present. Complete for a code execution tool.

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%, so schema already documents both parameters. Description adds no extra meaning beyond mentioning expression and arg, thus baseline 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?

Clearly states the tool executes arbitrary JavaScript in page context (page.evaluate()), with a specific verb 'execute' and resource 'JavaScript in the page context'. Distinguishes from sibling neko_click by specifying when to use this tool.

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?

Explicitly tells when to use this tool: when neko_click cannot trigger a client-side handler, giving a concrete example (ASP.NET PostBack). This provides clear guidance on alternatives.

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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