Browser Session MCP

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list_browser_sessions

Read-only

Lists every open browser session on the shared Chrome, sorted by session ID, including those opened by other agents. Use it to recover a lost session ID or find sessions left open.

Instructions

List every open browser session on the shared Chrome, sorted by sessionId, including ones opened by other agents; it takes no arguments. Use it to recover a lost sessionId or to find sessions left open; don't use it to see the tabs inside one session (list_pages) or saved logins (list_browser_states). activeUrl is null for a session with no tabs. The list is empty if none are open.

Input Schema

Name	Required	Description	Default
No arguments

Output Schema

Name	Required	Description	Default
`sessions`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv0.1.5Oct 24, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$defs": {
+    "SessionInfo": {
+      "properties": {
+        "activeUrl": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "pageCount": {
+          "format": "uint",
+          "minimum": 0,
+          "type": "integer"
+        },
+        "sessionId": {
+          "type": "string"
+        }
+      },
+      "required": [
+        "sessionId",
+        "pageCount"
+      ],
+      "type": "object"
+    }
+  },
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "properties": {
+    "sessions": {
+      "items": {
+        "$ref": "#/$defs/SessionInfo"
+      },
+      "type": "array"
+    }
+  },
+  "required": [
+    "sessions"
+  ],
+  "type": "object"
+}

First observedv0.1.2Oct 23, 2026

TDQS

A4.6/5.0

Behavior4/5

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds real context beyond them: cross-agent visibility, deterministic sort order, null activeUrl for tab-less sessions, and an empty list when nothing is open. It does not mention any cost or limit, but none is evidently needed for a zero-arg read.

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

Conciseness4/5

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

Front-loaded with the verb and scope, then siblings, then edge cases; every sentence carries information. It is dense, packing sort order, cross-agent scope, null semantics and empty-list behavior into a few clauses, but none of it is filler.

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?

An output schema exists, so return values need no prose, yet the description still clarifies the one ambiguous field (activeUrl null) and the empty-result case. For a zero-param read-only listing tool, an agent has everything needed to call it and interpret the result.

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 takes no parameters, which is stated explicitly ('it takes no arguments') and confirmed by an empty schema, so there is no parameter semantics to explain. Baseline for zero parameters 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?

States a specific verb and resource ('List every open browser session on the shared Chrome') plus scope details (sorted by sessionId, includes sessions opened by other agents). The sibling distinction is explicit: list_pages for tabs, list_browser_states for saved logins, so an agent can route without opening a schema.

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?

Gives both positive triggers ('recover a lost sessionId or to find sessions left open') and explicit exclusions naming the two alternative tools and what each is for. Nothing about when to choose this tool is left to inference.

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