Open File

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

With no annotations, the description carries the full behavioral burden. It only names the viewer behavior; it does not disclose permission requirements, whether it launches an external app and disrupts current app state, or what side effects follow. That is thin for an action-launching tool.

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 tightly written sentences, front-loaded with the action and followed by per-parameter guidance. Every clause carries information; there is 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?

An output schema exists, so return values need no explanation. However, the undocumented 'device' parameter and the absence of any side-effect or permission context leave gaps an agent would still need to resolve before calling confidently.

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%, so the description must compensate. It usefully documents uri (content://media/... format originating from find_files) and path ('a file under shared storage'), but the third parameter 'device' is undocumented, leaving part of the interface unexplained.

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 gives a specific verb and resource ('Open a file in its default viewer'), which clearly distinguishes it from lookup siblings like find_files. It does not explicitly name or contrast with alternative action tools (open_deeplink, system_intent), so it stops short of full sibling differentiation.

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 a strong sourcing rule for uri ('from find_files, never build one by hand'), which implies the intended workflow, but it never states when to prefer this tool over alternatives like open_deeplink or open_deep_link, nor any preconditions. Usage is implied rather than spelled out.

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