open_session

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

No annotations are provided, so the description must carry the burden. It does disclose that the session is stateful and uses a PTY by default, and that it returns a session ID. However, it omits behavioral details such as whether the subprocess runs continuously, how output is buffered, and whether the session requires explicit termination.

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 one sentence, immediately front-loads the core action, and contains zero filler. Every word adds value: 'stateful,' 'subprocess,' 'PTY by default,' 'returns a session id.'

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 tool that spawns a persistent process with six parameters and no annotations or output schema, a single sentence is insufficient. It doesn't explain the session lifecycle (e.g., use send/read to interact, close_session to terminate), parameter interactions, or error conditions. The description leaves critical context to the user to discover.

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 only 33% (pty and max_buffer_bytes have descriptions), requiring the description to compensate. The description adds little beyond what the schema already says; it does not explain cwd, env, args, or command semantics. The only param hint is 'PTY by default,' which duplicates the schema's pty description.

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 a specific action (spawn), resource (stateful subprocess session), and key detail (PTY by default). It distinguishes from sibling tools like tmux_open_session (which targets tmux sessions) and run (which likely executes a one-off command) by emphasizing the stateful session and returned session ID.

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 no guidance on when to use this tool versus alternatives like tmux_open_session for tmux workflows or run for quick commands. It does not mention prerequisites, lifecycle management (e.g., needing to close the session), or exclusions.

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