start_hmcl

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

No annotations are provided, so the description carries the full burden. It discloses several behavioral traits: headless (GUI never opens), idempotent (no-op if already running), and the specific return payload structure. This goes beyond the name and helps the agent predict side effects and output.

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 two sentences long and front-loaded with the core action. It packs essential details (headless, no-op, return fields, GUI behavior) without any filler. The mention of 'per ensureAgent' is slightly internal but does not detract from the overall efficiency.

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 tool with no output schema, the description is remarkably complete. It explains what happens, when it does nothing, what it returns, and how it interacts with the game window. This gives an agent all the information needed to invoke and interpret the result, especially given the sibling context.

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, so the schema coverage is effectively 100%. The description does not need to explain any parameter semantics. According to the rubric, the baseline for 0 parameters is 4, which is appropriate here.

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 it 'Start[s] the headless HMCL JVM with the injected javaagent' and returns agent status. The verb 'start' plus the specific resource distinguishes it from siblings like stop_hmcl or launch_game. It also notes the no-op behavior, adding further clarity.

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 clear context: this is a headless start that returns agent status, implying it is a prerequisite for launching games. However, it does not explicitly mention when to use it versus alternatives like launch_game, nor does it include exclusions. The purpose is obvious enough that an agent would know when to invoke it.

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