List or edit saved form-autofill addresses

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

Annotations already declare readOnlyHint=false and destructiveHint=true, and the description goes beyond them by documenting the actual backing module, confirming writability, and warning that storage may be served from the Rust store depending on extensions.formautofill.addresses.storage.rust.* prefs. It still does not say what remove does to existing data or whether it is recoverable.

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?

The purpose is front-loaded in the first sentence, but the 'MEASURED:' investigative narration and the aside about 'an earlier note' are meta-commentary that costs the agent reading time without helping it select or invoke the tool.

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 destructive, multi-action mutation tool with no output schema, the description covers writability and a backend caveat but omits what list returns, whether remove is irreversible, and whether add fails without required fields. Just enough to call it, not enough to call it confidently.

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 description coverage is 100% and already explains guid (for remove), the action enum, and the fields object with an example, so baseline is 3. The description adds no parameter-level detail beyond the schema.

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 a precise resource (saved form-autofill addresses), and explicitly excludes passwords, which distinguishes it from browser_list_logins and browser_autofill_status. It does not name any sibling tool outright, so it stops short of full sibling routing.

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?

The first sentence implies the use case (viewing or editing saved autofill addresses) but never says when to choose this over browser_autofill_status or the login tools, nor what prerequisites exist. The Rust-store note is context, not selection guidance.

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