Check if a spawned GUI program is still running and read the end of its output to diagnose a window that never appeared or a crash.
Whether a spawned program is still running, and the end of what it printed: for a window that never came up, or a crash.
| Name | Required | Description | Default |
|---|---|---|---|
| lines | No | How many lines from the end (40) | |
| program | Yes | Its name in the allow list | |
| session | Yes | Its name, from start_session |
Changes observed during successful MCP inspections.
v0.7.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds that it reports both liveness and trailing output, which is genuinely useful context, but it omits the tail-limit behavior (default 40, max 2000) and what is returned for an already-exited program.
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?
A single compact sentence with no filler, front-loading the primary return (running status). Slightly dense and grammatically choppy, but no wasted text.
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?
With no output schema, the description carries the return-value burden. It gestures at the two return components but does not specify the tail size, truncation, or behavior on non-running programs, leaving gaps for a diagnostic tool.
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 100% and each parameter (session, program, lines) already carries a description, so the baseline is 3. The description adds nothing about parameter semantics beyond what the schema documents.
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 two outcomes (running status and tail of printed output) but the phrasing is awkward ('the end of what it printed') and it never cleanly says 'returns the last N lines of a spawned program's output.' It is distinguishable from spawn/stop_session, but the scope is muddled.
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 implies a diagnostic use case ('for a window that never came up, or a crash') but does not say when to prefer it over alternatives such as wait_for, accessible_tree, or screenshot when diagnosing a program that failed to appear.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.