Open an app in a fresh phone-sized session and return its first screen.
| Name | Required | Description | Default |
|---|---|---|---|
| app | Yes | App id from list_apps, optionally with a release: 'tide' (local build), 'tide@latest' or 'tide@r13' (the published release phones run) | |
| dark | No | Dark mode | |
| session | No | Session name (default: generated). One session is one phone. | |
| seed_cart | No | Start with these items already in the cart (test shortcut). Each line: { product_id, quantity }; { id, qty } also works. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the behavioral burden. It usefully discloses that a fresh session is created and that the first screen is returned, but it does not explain session lifecycle effects, whether an existing session is replaced, cleanup expectations, or failure/auth behavior.
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?
It is a single, front-loaded sentence with no wasted text. The key action and immediate effect are stated efficiently.
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?
The schema is rich enough to support invocation, and the description states that the tool returns the first screen. However, with no output schema and no annotations, the return format and session side effects remain underspecified for an agent that needs to interpret the result 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?
Schema description coverage is 100%, so the schema already documents app identifiers, release syntax, dark mode, session naming, and seed_cart formats. The description adds no parameter-level meaning beyond what the schema provides, making the baseline score of 3 appropriate.
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 and resource: 'Open an app', and adds scope/effect with 'in a fresh phone-sized session and return its first screen'. It is clear without opening the schema, but it does not explicitly distinguish itself from siblings such as list_apps or screen.
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 mention of a 'fresh phone-sized session' implies the tool is for starting an isolated app session, but there is no explicit guidance on when to use this versus list_apps, screen, screenshot, or session-management tools. Usage is inferable rather than stated.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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