Open a live view of the game page

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

With no annotations, the description carries the full burden and does so well: it discloses that the server starts once per MCP process, frames are captured only while someone is watching, repeated calls return the same URL and never open a second tab, and it works with headless games. These are exactly the non-obvious traits an agent needs to avoid redundant or conflicting display actions.

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?

Front-loaded with the core action and the returned URL before the policy details, and every sentence carries substantive information. It is slightly long and repeats the open:true behavior that the schema already states, so not perfectly economical.

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 tool with no annotations and no output schema, the description covers what it does, what it returns, when to use it, exclusivity rules, and idempotency. Nothing an agent needs to invoke it correctly is missing.

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 100%, so both parameters are already documented. The description still adds operational meaning for 'open' ('also launch the URL in the default browser') and the constraint 'at most once per game', going slightly beyond the schema, though the core param semantics remain schema-driven.

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?

States a specific verb and resource: it starts a local web server that streams JPEG screenshots of the real Playwright tab along with passage/step/engine state. It distinguishes itself from the sibling 'screenshot' by being a continuous streaming view rather than a one-off capture, and names the return value (a URL).

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 DISPLAY POLICY block explicitly states when to use it ('this is the default — and usually the only — way to show a game') and when not to ('do not also switch to a headed window or loop screenshot'). It also names the idempotent alternative behavior of repeated calls, so an agent has no ambiguity about routing.

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