open_url

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

With no annotations, the description carries full responsibility for disclosing behavior. It only states the basic action and provides no insight into side effects (e.g., browser focus, network activity), error handling, or whether the call is synchronous. This is a significant gap for a tool that has external side effects.

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?

The description is extremely concise (one sentence plus a redundant args line), front-loading the purpose. There is no wasted text, but the redundant parameter repetition mildly detracts from efficiency.

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 single-parameter tool this simple, the description covers the core purpose and parameter. However, it lacks usage context, behavioral detail, and failure semantics. The presence of an output schema mitigates some return-value ambiguity, but overall the description is merely functionally adequate.

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 input schema has 0% coverage from the description, so the description must compensate. It merely repeats 'URL to open' without adding format details (e.g., http/https requirement), validation rules, or examples. The description adds no value beyond the schema's 'url' title.

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 clearly states the action ('Open a URL') and the target ('default browser'), which is specific and distinguishes it from sibling tools like open_file or launch_app. The verb+resource combination is unambiguous.

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 implies when to use the tool (to open a URL in the default browser) but provides no explicit guidance on when to choose it over alternatives, nor any exclusions. It relies on the user's inference from the tool name and description.

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