open_lab

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

With no annotations, the description carries full burden. It discloses that the tool creates/reuses a sandbox, binds it to the session, and optionally auto-joins a viewer. This is useful context, though it does not mention potential side effects like resetting an existing session or permission requirements.

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 short paragraphs, each serving a distinct purpose. The first states the core behavior and prerequisite; the second adds a conditional environment-specific behavior. No filler or redundancy.

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 single-parameter tool with an output schema, the description adequately covers the action, prerequisite, and optional viewer behavior. It gives the agent enough to invoke the tool correctly without needing external 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?

Schema coverage is 0%, but the description fully compensates by explaining the `path` parameter: it's the lab file name with NO leading slash, and provides a concrete example ('2pc_1sw.unl'). This is far more informative than the bare schema.

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 'Open a lab for editing/running' with a specific resource ('lab'), and distinguishes this from sibling tools like get_lab or close_lab by explaining it creates/reuses a sandbox and binds it to the session. The example path further anchors the purpose.

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?

It explicitly states 'Must be called before add_node / start_node / get_lab / etc.', providing clear sequential guidance. It also gives context about auto-joining a viewer account when PNETLAB_VIEWER_USERNAME is configured, which tells the agent when an additional behavior occurs.

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