Browser Session MCP

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list_browser_states

Read-only

Lists saved browser states (cookie sets) accepted by load and delete actions, sorted by name, so you can choose a saved login to load. Returns an empty list if none are saved.

Instructions

List the saved browser states (cookie sets saved by save_browser_state) that load_browser_state and delete_browser_state accept, sorted by name; it takes no arguments and changes nothing. Use it to pick a name to load; these are saved logins on disk, not open sessions, so use list_browser_sessions for those. The list is empty if nothing has been saved.

Input Schema

Name	Required	Description	Default
No arguments

Output Schema

Name	Required	Description	Default
`states`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv0.1.5Oct 24, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$defs": {
+    "StateSummary": {
+      "properties": {
+        "cookieCount": {
+          "format": "uint",
+          "minimum": 0,
+          "type": "integer"
+        },
+        "name": {
+          "type": "string"
+        },
+        "savedAt": {
+          "type": "string"
+        }
+      },
+      "required": [
+        "name",
+        "savedAt",
+        "cookieCount"
+      ],
+      "type": "object"
+    }
+  },
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "properties": {
+    "states": {
+      "items": {
+        "$ref": "#/$defs/StateSummary"
+      },
+      "type": "array"
+    }
+  },
+  "required": [
+    "states"
+  ],
+  "type": "object"
+}

First observedv0.1.2Oct 23, 2026

TDQS

A4.9/5.0

Behavior5/5

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

Annotations already declare readOnlyHint=true and openWorldHint=false, and the description adds useful context: the tool takes no arguments, changes nothing, sorts by name, returns an empty list when nothing is saved, and represents saved logins on disk rather than open sessions. This goes beyond the annotations and clarifies behavior that matters for selection.

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 front-loaded with the core purpose, then adds disambiguation and edge-case behavior in a compact form. Every sentence contributes useful selection or invocation 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?

For a simple no-parameter read tool with an output schema and clear annotations, the description is complete. It explains the resource, sibling distinction, usage, sorting, empty-state behavior, and lack of side effects.

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 schema has zero parameters at 100% coverage, so there are no parameter semantics to explain. The description correctly notes that it takes no arguments, which is the only relevant parameter-level detail; the baseline for zero parameters is 4.

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 a specific verb and resource: list saved browser states, defined as cookie sets saved by save_browser_state and accepted by load_browser_state/delete_browser_state. It also distinguishes this from list_browser_sessions, so an agent can differentiate it from siblings immediately.

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?

It explicitly says to use this tool to pick a name to load, and directs the agent to list_browser_sessions for open sessions. That covers the key when-to-use and when-not-to-use case among the siblings.

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