open_file

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

With no annotations, the description fully discloses behavioral traits: it opens on existing display, runs specified app or xdg-open, resolves relative paths, returns specific fields, fails if file/app doesn't exist, starts asynchronously (suggesting screenshot confirmation), and notes GTK apps get same handling as launch_app. No contradictions.

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 reasonably concise with two paragraphs. The first sentence front-loads the core purpose and key constraint. Every sentence serves a purpose, though the structure could be slightly more streamlined (e.g., grouping related details).

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?

Given the complexity (3 params, no annotations, output schema exists), the description is complete: it covers purpose, usage guidelines, parameter behavior, failure modes, async nature, and alternatives. The output schema is referenced by naming returned fields, fulfilling completeness.

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?

Despite 0% schema description coverage, the description adds meaningful semantics: it explains the app parameter (optional, runs that app), filepath (required, resolves relative to staging folder), and implicitly references instance (existing display). It does not detail the instance parameter's type or default, but the schema covers those.

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 clearly states the tool opens a local file in an app on an existing instance's display, explicitly distinguishing it from creating a new instance. It specifies the exact resource (local file) and context (existing display), making the purpose unambiguous.

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 provides explicit guidance on when to use this tool versus alternatives: it says to use upload_file() for browser file uploads, and contrasts with launching a new instance. It also explains relative path resolution against the instance's staging folder, referencing list_files for context.

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