open_url

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

Annotations declare readOnlyHint=false and destructiveHint=false, so the safety profile is already covered. The description adds the meaningful detail that the page opens in the default browser, but says nothing about return value, whether tabs are reused, or what happens if no browser is available. With annotations carrying the safety burden, a 3 is appropriate.

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?

One front-loaded sentence states purpose, and the Args block is short. The Args repetition of the single param name is mildly redundant but conventional and not wasteful.

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 one-parameter action with annotations and no output schema, the definition covers what the agent needs: the action, the target, and the required URL format. It omits side-effect/return behavior, which is a minor gap given the tool's simplicity.

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 0% and the schema only declares a bare string, so the description carries the parameter burden. It compensates by specifying "A full http:// or https:// URL," which adds a real format/scheme constraint not present in the schema. Full compensation for a single simple param, short of a 5.

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 ("Open a web page") and narrows scope with "in the default browser," which separates it from siblings like open_file, open_app, and download_url. It does not name a sibling it is distinct from, so it falls 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?

No when-to-use guidance, no exclusions, and no routing to alternatives such as download_url (save the resource) or read_browser_tab (fetch content) despite many plausibly related siblings. The agent must infer when opening a URL is the right call.

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