Skip to main content
Glama
mozilla

firefox-devtools-mcp

by mozilla
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Local

new_page

Open a new tab at a specified URL and return its tab index. Use optional wait states to control when navigation completes.

Instructions

Open new tab at URL. Returns tab index.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
urlYesTarget URL
waitNoWhen to return: 'none' (navigation started), 'interactive' (DOMContentLoaded), 'complete' (load event fired, including subresources). Omit for the default: 'interactive' for http/https/data/blob/file, 'none' for other schemes. Use 'complete' when the page must be fully loaded, e.g. before stopping a performance recording.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv0.10.3
    • addedInput schema / properties / wait
      Added value: +{
+  "description": "When to return: 'none' (navigation started), 'interactive' (DOMContentLoaded), 'complete' (load event fired, including subresources). Omit for the default: 'interactive' for http/https/data/blob/file, 'none' for other schemes. Use 'complete' when the page must be fully loaded, e.g. before stopping a performance recording.",
+  "enum": [
+    "none",
+    "interactive",
+    "complete"
+  ],
+  "type": "string"
+}
  2. Changed1 schema field changedv1.0.0
    • changedInput schema / properties / url / description
      Previous value: -"URL to load in a new page"New value: +"Target URL"
  3. First observed

TDQS

B3.2/5.0
Behavior2/5

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

Annotations only provide readOnlyHint=false, which minimally signals a mutation. The description adds 'returns tab index' but does not disclose whether the new tab becomes active, how it affects the current tab, or other side effects. For a browser automation tool, this is a significant transparency gap.

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 sentences with no wasted words. It front-loads the purpose and return value, earning its place.

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

Completeness2/5

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

The description is incomplete for browser automation: it doesn't clarify whether the new tab becomes active, how the returned index should be used with tools like select_page, or any behavioral caveats. The return value is mentioned but not contextualized.

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 description coverage is 100%, and the wait parameter has detailed semantics in the schema itself. The description only reiterates 'URL' without adding new meaning, so the baseline of 3 applies.

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 states the specific action (open a new tab), the resource (a URL), and the return value (tab index). This clearly distinguishes it from sibling tools like navigate_page (which likely operates on the current tab) and select_page (which changes the active tab).

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

Usage Guidelines2/5

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

The description gives no guidance on when to use this tool versus alternatives like navigate_page or select_page. It implies the use case (creating a new tab) but does not mention exclusions, prerequisites, or scenarios where another tool would be more appropriate.

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

Deploy Server

Other Tools