android_open_uri

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

Given the annotations already include destructiveHint=true, the description adds non-obvious behavioral context: the tool uses Android intents and does not directly place a call even for tel URIs. This helps the agent understand the side-effect profile beyond what annotations alone convey. No contradiction with annotations exists.

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 only two sentences long, with no filler. The action and accepted URI schemes are front-loaded, and the important behavioral caveat about not placing a direct call is placed at the end.

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 with no output schema, the description fully covers what the tool does, what inputs it accepts, and a key behavioral nuance. An agent has enough information to select and invoke this tool correctly.

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 schema only defines uri as a string with length limits, so the description adds essential meaning by enumerating allowed URI schemes: http(s), geo, tel, mailto, and sms. It tells the agent what kind of value to supply, though it could have included concrete URI examples.

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 uses a specific verb plus resource: 'Open an http(s), geo, tel dialer, mailto or sms URI using Android intents.' It clearly distinguishes this from sibling tools like android_launch_app or android_share_text by defining exactly which URI schemes it handles.

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 clearly communicates when to use the tool: when the target is a supported URI scheme. It also provides a useful exclusion by stating 'This does not directly place a call,' which prevents the agent from using it to place calls directly. It does not explicitly name alternatives or sibling tools.

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