Open URL

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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=true, so the mutation/external-reach profile is covered. The description adds real behavioral value beyond that: it discloses scheme validation, the rejection behavior, and the MOBILEMCP_ALLOW_UNSAFE_URLS=1 escape hatch.

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 sentences, zero filler, with the core action front-loaded and the constraint following immediately. Every clause 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 two-parameter tool with full schema coverage and annotations covering the safety profile, the description supplies purpose, accepted input domain, and failure mode. No output schema exists and none is needed for a fire-and-forget navigation action.

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%, so both parameters (url, device) are already documented in the schema, including the http/https requirement and the pointer to mobile_list_available_devices. The description's scheme constraint largely restates the url parameter description, so it adds only marginal 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 and resource ('Open an http:// or https:// URL in the browser on device') and constrains the accepted scheme inline. This is readily distinguishable from siblings like mobile_launch_app, which handles app launching rather than URL opening.

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 gives a clear negative condition (non-http/https schemes such as app deep links are rejected unless the env flag is set), which tells the agent when the call will fail. However, it never names an alternative tool for the deep-link/app-launch case, so routing guidance is only implied.

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