Read the default search engine

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

Annotations already declare readOnlyHint=true, and the description corroborates that with the reason (the SearchService ES module is unreachable, every resource:// path fails), which is genuinely additive context an agent cannot get elsewhere. It also discloses the underlying data sources, though it does not describe the return shape, ordering, or what happens if search.json.mozlz4 is missing or unreadable.

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 sentences, front-loaded with what is returned and followed by the read-only caveat; the pref key and file name are concrete rather than padded. It is slightly dense but no sentence is filler.

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?

With no output schema and no parameters, the description does the necessary work by naming the two returned pieces of information and explaining the read-only constraint. Only the failure behavior for a missing or unparseable search settings file is left unaddressed.

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?

The tool takes zero parameters, so the schema carries no semantics burden and the baseline applies. Nothing in the description needs to explain inputs, and it correctly does not invent any.

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?

The description names a specific verb (report) and specific resources (the default search engine pref and the engine list from search.json.mozlz4), so its function is unambiguous. It stops short of distinguishing itself from the nearby siblings browser_search_engine, browser_search_prefs, or browser_add_search_engine, which a reader must resolve by inference.

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 context is only implied: the LIMITATION sentence tells the agent that changing the default engine is out of scope, which hints that a different route is needed for mutation. It never explicitly says 'use browser_search_engine (or browser_set_pref) to change it' or otherwise routes the agent to an alternative, and there are no stated preconditions.

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