Open a URL or file on Android

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

Annotations already declare openWorldHint=true and non-readonly/non-destructive behavior, and the description adds genuinely new context: paths are resolved on-device and Android permissions still apply, which warns of possible failure outside the tool's control. It doesn't describe what a success/failure response looks like, and there is no output schema to cover that gap.

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, front-loaded with the primary URL case, then the file case, then the caveat. No filler.

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 launcher, the description plus annotations cover mechanism, scope, and permission risk adequately. It could be more complete by noting that the open happens in an external app (no return value or confirmation from the tool).

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 are already documented with examples (the 'text/plain' MIME example for content_type). The description only implies the target accept-forms already stated in the schema and adds nothing about content_type handling.

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?

Specific verb + two concrete resources: 'Open an http(s) URL in the default browser, or open a local file with Android via Termux:API.' An agent immediately knows this launches external handlers rather than reading/returning content, which separates it from read_file or run_command.

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?

It gives clear usage context by mapping each input form (http(s) URL vs. local path) to the resulting behavior, so an agent knows when this tool applies. It stops short of explicit exclusions, e.g. pointing to read_file when the goal is to inspect a file's contents rather than launch it.

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