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Chrome Bridge

Chrome Bridge

by frsorrentino
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JavaScript
Local

session_fixture

DestructiveIdempotent

Save, restore, or list session fixtures capturing localStorage, sessionStorage, and cookies for the current origin to reuse logged-in states.

Instructions

Snapshot localStorage, sessionStorage and cookies of the current origin into a named fixture (a logged-in state, usually), restore one, or list them. save overwrites silently; restore writes on top without clearing and refuses on a different origin — cookies would attach to the wrong site.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "action": "<action>"
    },
    "name": "session_fixture"
  }
}

Input Schema

NameRequiredDescriptionDefault
nameNoRequired for save/restore
actionYessave snapshots the current origin; restore writes it back
tab_idNoTarget tab; omitted = last tab navigated in this session, else the active one

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changedv1.10.0
    • addedInput schema / properties / action / description
      Added value: +"save snapshots the current origin; restore writes it back"
    • addedInput schema / properties / tab_id / description
      Added value: +"Target tab; omitted = last tab navigated in this session, else the active one"
  2. First observedv1.8.0

TDQS

A4.1/5.0
Behavior5/5

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

The description is highly transparent about side effects: 'save overwrites silently' and 'restore writes on top without clearing' explicitly warn about destructive behavior, and the origin restriction is explained. This aligns with the destructiveHint annotation and adds specific detail beyond it.

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 concise, using two well-structured sentences. It packs all necessary information without redundancy or filler, making it easy to parse quickly.

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?

The description covers core functionality and safety caveats, but does not mention any return values or error cases beyond the origin refusal. Since there is no output schema, the agent might not know what 'list' returns. Still, for a simple tool, the given context is mostly sufficient.

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 parameter descriptions add meaningful context: 'name' is explained as required for save/restore (though optional in schema), 'action' describes save and restore semantics, and 'tab_id' is clear. However, the 'list' action is not explicitly described, and the conditional requirement for 'name' could be clearer. Since schema coverage is 100%, this is above baseline.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's three actions (snapshot, restore, list) and specifies it targets localStorage, sessionStorage, and cookies for the current origin into a named fixture. However, it doesn't explicitly differentiate itself from similar sibling tools like get_storage or set_storage, which might cause some ambiguity.

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

Usage Guidelines3/5

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

It provides useful behavioral context (e.g., 'restore refuses on a different origin') but does not explicitly state when to use this tool over alternatives like session_record or get_storage/set_storage. The condition 'logged-in state' gives some guidance, but a clearer comparison to siblings would improve the score.

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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