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nzjami

Playwright MCP

by nzjami

browser_navigate_back

Destructive

Navigate back to the previous page in the browser during automation workflows. Use this tool to return to prior web pages when testing or interacting with websites programmatically.

Instructions

Go back to the previous page

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Implementation Reference

  • The main handler function that performs the browser back navigation by calling `tab.page.goBack()`, includes a snapshot in the response, and adds corresponding Playwright code snippets.
    handle: async (tab, params, response) => {
      await tab.page.goBack();
      response.setIncludeSnapshot();
      response.addCode(`// Navigate back`);
      response.addCode(`await page.goBack();`);
    },
  • Zod schema definition for the tool, specifying name, title, description, empty inputs (no parameters), and readOnly type.
    schema: {
      name: 'browser_navigate_back',
      title: 'Go back',
      description: 'Go back to the previous page',
      inputSchema: z.object({}),
      type: 'readOnly',
    },
  • src/tools.ts:44-44 (registration)
    Registers the browser_navigate_back tool by spreading the exports from navigate.ts into the central allTools array used by the system.
    ...navigate,
  • Exports the defined goBack tool (browser_navigate_back) as part of the module's default export array for inclusion in the tools registry.
    goBack,

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

A4.4/5.0
Behavior4/5

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

Annotations provide readOnlyHint=false, openWorldHint=true, and destructiveHint=true, indicating this is a mutable, potentially destructive action with open-world behavior. The description adds value by specifying 'previous page,' which clarifies the scope of the action beyond what annotations convey. However, it doesn't detail side effects like history changes or potential page reloads, so it's not fully comprehensive but still adds useful context without contradicting annotations.

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 'Go back to the previous page' is a single, efficient sentence that is front-loaded with the core action. It wastes no words and directly communicates the tool's function, making it highly concise and well-structured for quick understanding.

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?

Given the tool's low complexity (0 parameters, no output schema) and rich annotations (covering safety and behavior), the description is mostly complete. It specifies the action and target, but could benefit from mentioning potential outcomes like navigation failure or history state. However, with annotations handling key behavioral aspects, the description is adequate for the context, though not exhaustive.

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 input schema has 0 parameters with 100% coverage, so no parameters need documentation. The description doesn't add parameter details, which is appropriate here. A baseline of 4 is applied as per the rules for 0 parameters, since the description doesn't need to compensate for any schema gaps and aligns well with the empty schema.

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 'Go back to the previous page' clearly states the action (go back) and the resource (previous page) with a specific verb. It distinguishes this tool from siblings like 'browser_navigate' (which goes to a new page) and 'browser_tabs' (which manages tabs), making the purpose unambiguous and well-differentiated.

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 implies usage context (when you want to return to a previous page in browser navigation), but does not explicitly state when NOT to use it or name alternatives. For example, it doesn't specify that this should be used instead of 'browser_navigate' for backward navigation or mention prerequisites like requiring a browser session with history. The context is clear but lacks explicit exclusions or named alternatives.

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