mujoco_open_viewer

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

Annotations already declare idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context: the window starts paused, there is a one-window-per-server constraint, and it does not attach to the standalone app. It also mentions macOS launch requirements. This goes beyond the annotations without contradicting them.

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 compact and front-loaded: the core purpose is in the first sentence, followed by essential usage constraints and platform notes. Every sentence earns its place, and there is no fluff.

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 tool has a simple input schema (one required parameter) and an output schema exists, so the description doesn't need to explain return values. The description covers the key behavioral constraints (paused start, one-window limit, standalone app distinction, macOS launch). It could explicitly state that session_id is the session to open, but the overall context is sufficient for an agent to call it 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 0%, so the description must compensate for the single parameter session_id. The description mentions 'this session's model and state' but does not explicitly explain that session_id identifies which session's model/state to display. However, with only one parameter and a clear name, the meaning is largely inferable. The description adds some context but not a full parameter explanation.

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 ('Open') and resource ('native MuJoCo window sharing this session's model and state'), and distinguishes it from the standalone DMG app. It clearly identifies what the tool does and is distinct from siblings like mujoco_close_viewer.

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 when-to-use guidance: 'Starts paused; call mujoco_step or mujoco_set_running next' and 'One window per server: close the current viewer before displaying another session.' It also tells the user what not to do ('does not attach to the standalone DMG app') and gives platform-specific launch instructions. This is strong usage guidance.

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