Green flag

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

With no annotations provided, the description carries the full burden and it succeeds: it discloses side effects (clearing bubbles, pending question, errors) and confirms it does not advance time. This gives the agent the necessary behavioral expectations for a state-changing action.

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 sentences, with the main action and side effects in the first sentence, and the critical usage contrast and prerequisite in the second. No filler; every clause adds value.

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 zero-parameter action with no output schema, the description fully covers what the tool does, its effects, what it does not do, and prerequisites. An agent can invoke it correctly with no further information.

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 tool has zero parameters, and the schema correctly reflects that with no properties. The description doesn't need to explain parameters; the baseline of 4 for no-parameter tools is appropriate, and no additional semantics could be added.

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 states a specific verb ('Press the green flag') and resource ('headless runtime'), and explains the exact effects (clears bubbles, pending question, errors, starts scripts). This clearly distinguishes it from sibling tools like vm_run and vm_load, which have different actions.

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?

Explicitly says what the tool does NOT do ('Does not advance time on its own') and directs the agent to vm_run for stepping, and vm_load as a prerequisite. This leaves no ambiguity about when to use this tool versus alternatives.

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