Read a single localStorage value from the current browser page using a session ID and key to retrieve stored client-side data.
Read one localStorage value in the current page context.
| Name | Required | Description | Default |
|---|---|---|---|
| key | Yes | Storage key to read | |
| session_id | Yes | Session ID returned by browser_navigate |
Changes observed during successful MCP inspections.
v2.15.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so safety is covered. The description adds the 'current page context' scoping detail, but does not say what happens if the key is missing or the page isn't loaded. With annotations doing the heavy lifting, a 3 fits.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
A single sentence with no waste, front-loaded with verb and resource. The 'current page context' qualifier earns its place by scoping behavior.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple two-parameter read tool with full schema coverage and annotations declaring safety, the description is nearly complete. The only minor gap is not stating the result when a key is absent (null/error), which would help an agent interpret the call.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100%, so both session_id and key are fully documented in the schema, and the description adds no format or syntax detail beyond it. The phrase 'one localStorage value' subtly confirms single-key semantics, matching the 'key' parameter, but this is baseline-level added value.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb (Read) and resource (localStorage value) with scope qualifier 'one' and 'current page context'. This distinguishes it from browser_set_local_storage and browser_clear_local_storage, which mutate rather than read, though neither sibling is named explicitly.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Usage is implied by the read-vs-write/clear split among the localStorage siblings, but the description never states when to prefer this tool or what conditions apply (e.g., must be on a page, key must exist). No explicit alternatives are named.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.