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playwright-mcp-server

playwright-mcp-server

by doucej
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Local

save_state

Save current browser session to disk, preserving cookies, localStorage, and active URL, so the state reloads automatically when the server restarts.

Instructions

Persist the current browser session (cookies, localStorage, active URL) to disk. The state is reloaded automatically on server restart.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "save_state"
  }
}

Input Schema

NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.0.0

TDQS

A4.5/5.0
Behavior4/5

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

Without annotations, the description carries the burden of behavioral disclosure. It explains what data is persisted and that the state is automatically reloaded on restart, which is useful beyond the tool name. However, it does not mention whether existing saved state is overwritten or any permissions needed, so it is not perfectly transparent.

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?

The description is two concise sentences. The first sentence leads with the main action and details, the second adds the key behavioral note about auto-reload. No redundant or unnecessary words.

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?

For a simple parameterless tool, the description covers the essential aspects: what is saved, where it is saved (to disk), and what happens on restart. It is complete enough for an agent to understand when and how to use the tool, and the sibling 'load_state' completes the picture.

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?

The tool has zero parameters, so there is no parameter information to add. The baseline for no parameters is 4, and the description does not attempt to describe nonexistent parameters.

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?

The description clearly states the action ('Persist the current browser session to disk') and specifies the exact data captured (cookies, localStorage, active URL). It distinguishes this from its sibling tool 'load_state' by describing the persistence rather than restoration.

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?

The description provides clear context: this saves state so it can be automatically reloaded on server restart. It does not explicitly name alternatives or exclusions, but the intended use case (persistence) is evident from the text and the sibling tool list.

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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