Storage & application data

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

With annotations only declaring readOnlyHint=false and openWorldHint=false, the description adds real context: it explicitly flags that set/remove/clear are writes (destructive on stored data) and that cookie reads include HttpOnly cookies, a security-relevant capability worth calling out. It still omits whether writes are reversible or whether elevated permissions are needed per area.

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?

Front-loaded with the core purpose, then a dense but well-structured area enumeration and an action/semantics clause. No filler sentences; the only cost is that the second half reads as a compressed glossary rather than scannable structure.

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 13-parameter, no-output-schema tool the description covers the input space well because the schema is fully annotated, but it says nothing about what list vs get returns, how `limit` pagination behaves across areas, or which areas support which actions. An agent can call it, but may pick an invalid area/action combination.

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 baseline is 3, but the description adds meaning the schema does not: it maps `url`/`domain` to cookie scoping, explains the nested path in indexeddb (databases, stores, records) so `key` as "db/store" makes sense, and states the read/write split for `action`. Minor gain over a fully documented schema, not a major one.

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?

Names a specific verb pair (reads and edits) plus a concrete resource domain, then enumerates every `area` value with a short gloss (cookies, local/session, indexeddb, cache, serviceworkers, manifest, quota). The 'like the DevTools Application panel' anchor lets an agent distinguish it immediately from dom_inspect, network_requests, or console_logs.

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 action taxonomy ('list/get read, set/remove/clear write') gives implied guidance on which action to pick, and the area glosses hint at when each area applies. However, there is no explicit when-to-use vs siblings (e.g., versus evaluate or dom_inspect) and no warning that write actions only make sense for some areas (cookies, local, session, cache) while others are read-only (serviceworkers, manifest, quota).

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