Switch the active theme

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

Annotations already declare readOnlyHint=false and destructiveHint=true; the description adds real context beyond them by explaining the mechanism (the add-on enable path, same as clicking Enable in the Add-ons manager) and that the effect is immediate. It also supplies a recovery path (default:true). It does not say the previously active theme is deactivated or whether there is any failure mode, which is the remaining gap.

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?

Three short sentences, front-loaded with the primary action and mode switch before the mechanism rationale. Every sentence adds information; nothing is padding.

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 two-parameter, no-output-schema switch tool with full annotation coverage, the description gives enough to call it correctly, including the id source and a reset option. The only omission is the zero-argument edge case, which is minor here.

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%, so both parameters are already documented in structured data and the description only restates the id source and the default flag. Neither required parameter means an agent could call this with no arguments, and the description never says whether that errors or is a no-op — a meaningful semantic gap the schema also leaves open.

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 and resource ("Activate one of the installed themes by id") plus the reset variant via default:true, so the operation is unambiguous. It points at browser_list_themes as the id source but never mentions when the generic sibling browser_set_addon_state would be the better choice, so sibling differentiation is only partial.

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?

Explicitly covers both invocation modes: activate an installed theme by id, or pass default:true to return to the default theme. That is clear operative guidance, but there are no exclusions or prerequisites (e.g. what happens if the id refers to a disabled/removed theme).

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