session_open

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

No annotations are provided, so the description carries the burden, and it discloses two non-obvious behaviors: it starts a live browser view for a human observer, and its return value is a literal 24x80 screen plus a field list. It does not mention cleanup via session_close or failure behavior, but the key side effects and return contract are named.

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 no filler. The main action is front-loaded, followed by the browser side effect and the return contract, so every sentence earns its place.

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 description defines the return value, names the browser side effect, and references the downstream tool, which is strong for a tool with no output schema. It omits explicit lifecycle guidance such as closing the session with session_close or behavior when reopening the same session name, leaving a small but real gap.

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 schema already documents all 7 parameters with 100% coverage, so the description does not need to add per-parameter meaning. It usefully ties output field refs to screen_do, but that is output-oriented rather than parameter-oriented, matching the baseline for fully covered schemas.

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 opens with a specific action and resource: 'Open a 5250 session to an IBM i and sign on, then return the first screen.' It also differentiates from siblings by defining the return artifact as a screen snapshot with field refs meant for screen_do, so an agent can tell it apart from screen_snapshot and screen_do.

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 establishes clear context: use it at the start of a session, and the returned field refs are explicitly tied to screen_do, giving natural next-step guidance. It does not explicitly state when not to use it (e.g., if a session already exists, prefer screen_snapshot), so it stops short of full exclusion criteria.

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