Set the homepage and startup behaviour

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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the mutation profile is known. The description adds real context by mapping startupPage to the numeric pref values, but never says that an existing homepage value is overwritten, that the change persists in the profile, or whether a restart is required — gaps that matter for a destructive tool.

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, front-loaded sentences with zero filler: the mutation target and format come first, the exception case last. Every clause carries information.

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-optional-parameter tool with a full schema and annotations covering the destructive profile, the description is nearly sufficient — the enum-to-pref mapping is a nice bonus. The remaining hole is what happens to an existing homepage and whether the setting takes effect without a restart.

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 both parameters are documented there, so baseline is 3. The description restates the newline-separated homepage format and the four startupPage values already enumerated in the schema, adding only the underlying pref value mapping as marginal extra meaning.

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 ('Set') and resource (homepage plus startup behaviour), and names the underlying pref keys browser.startup.homepage / browser.startup.page, which implicitly distinguishes it from the generic browser_set_pref sibling. It does not explicitly say why to prefer it over browser_set_pref, so it stops short of a 5.

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 closing sentence 'Pass only homepage to leave the startup behaviour alone' gives one useful usage rule for the optional-parameter case. However, there is no guidance on when to use this tool versus browser_set_pref or browser_save_session/browser_restore_session, which are the obvious alternatives for startup behaviour.

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