Get or set the default browser

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

With no annotations present, the description bears the full burden of disclosing behavior and does so well: it reveals the read-vs-write mode distinction and warns that changing the handler 'may make macOS ask the user to confirm' — a side effect an agent needs to anticipate. It could add what the report output looks like, but for a dual-mode tool, this is strong disclosure.

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 front-loaded sentences accomplish everything: stated purpose, mode explanation, and a caveat. No filler or redundancy — every sentence earns its place.

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 simple 1-parameter tool with no annotations and no output schema, the description is largely complete. It covers purpose, invocation modes, and side effects. The only minor gap is omitting what the tool returns when reporting, but without an output schema requirement, this is a small miss.

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% with a clear bundleId description. The description adds value by linking the parameter to behavior via 'Omit to only report,' reinforcing the conditional nature of the argument beyond the schema alone. This pushes it slightly above the baseline-3 for full schema coverage.

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 uses a specific verb-resource pairing: 'Report which application handles http, https, and mailto links' with the modifier 'optionally change.' It clearly covers both execution modes and the exact URL schemes in scope. The tool has no near-namesake siblings, and the description's coverage of the dual report/modify behavior fully disambiguates it.

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 description explicitly explains the tool's two modes with 'Called with no arguments it only reports' and how to invoke the change behavior. It provides clear when-based context for a single-argument workflow. It stops short of explicitly naming alternatives or excluded scenarios, though no sibling tool directly overlaps, so the guidance is sufficient for correct selection.

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