Read or write an extension private storage

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

With only readOnlyHint=false available, the description earns credit by disclosing the mechanism: a background tab is opened on an extension page, the call runs in that page context, and the tab is closed. It also flags a measured reachability limitation. It stops short of saying what mutating actions destroy or what read returns.

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?

Two dense sentences: the first defines the resource and scope, the second explains the mechanism and its limitation. No filler, and the identifying information is front-loaded.

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 four-parameter tool with no output schema, the description covers the mechanism, the prerequisite, and the failure mode well. The main remaining gap is what a read returns (shape of the key/value result), which would help an agent plan the follow-up 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 id, keys, data, and the action enum are already documented in the schema. The description adds context for the storage namespace but no parameter-level meaning (e.g., which actions require data or keys, or key semantics). Baseline 3 is appropriate.

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 pair (read/write) and resource (extension private key/value storage, browser.storage.local) with the added clarification that it holds settings and lists. It is distinguishable from siblings like browser_extension_details or browser_run_in_extension, though it never names those alternatives 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 resource description, and a hard constraint is given (extensions without an options page cannot be reached). However, there is no explicit when-to-use versus browser_run_in_extension or browser_extension_details, and no guidance on which action to pick for a given goal.

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