open_url

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

With no annotations supplied, the description carries the full behavioral burden. It does disclose one genuinely useful trait beyond the schema — that the URL may be handed off to a matching app rather than always opening in a browser — but says nothing about foreground/background behavior, permission prompts, failure modes, or whether the call blocks.

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?

A single front-loaded sentence with zero waste; the parenthetical is the one piece of clarifying detail that 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?

The tool is simple enough (one string parameter, no output schema) that a one-liner is close to adequate. But with no annotations and no output schema, the description should still cover what a successful call looks like and how bad input or app-routing failure surfaces, which it omits.

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 0% for the single parameter, so the description must compensate and does not. It never says whether 'url' requires an https:// scheme, whether custom app schemes (e.g. youtube://) are accepted, or how URLs are matched to apps — all of which matter for the only input.

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 URL on the phone') and clarifies the routing behavior — browser or a matching app such as YouTube. It is distinguishable from open_app by operating on a URL rather than an installed app, though it never names that sibling explicitly.

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 guidance on when to prefer this over open_app (e.g. deep links vs app launch) or over shell. There is also no guidance on URL format, required scheme, or what happens on an invalid or unsupported URL, leaving the agent to infer everything about selection.

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