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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds useful behavior beyond that: results come 'from the pool alone' (no external fetch), nothing is persisted ('nothing is saved'), and empty lanes are explicitly reported ('a quiet lane says so').

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 single run-on sentence is dense and poetic rather than front-loaded, with phrases like 'the main it was ranked by' forcing the reader to decode intent. It is short in word count but poorly structured for an agent scanning for purpose and behavior.

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?

An output schema exists, so return values need not be explained, and annotations cover safety. The description still leaves 'lane' undefined and does not clarify how the language parameter affects output or how this tool relates to morning/my_brief, so it is only adequately complete for a three-parameter 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 coverage is 67%; the schema itself explains the brief format and resolution of plain names, and days is self-documented. The description only echoes the time window ('the last days') and adds no meaning for the language parameter, so it adds marginal value beyond the structured 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 conveys a dry-run preview: 'the mornings of the last days the brief would have given, lane by lane' indicates replaying what a brief would have produced over past days. However, the phrasing is oblique, and it never plainly states the verb (rehearse/preview) or distinguishes itself from siblings like morning, my_brief, or save_brief beyond the closing 'nothing is saved'.

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?

There is no explicit when-to-use or when-not-to-use guidance, and no sibling is named as an alternative. The phrase 'nothing is saved' hints at a dry-run contrast with save_brief/set_brief, but the agent must infer that rather than being told.

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