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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the bar is lower; the description still adds real value by disclosing the window semantics (since the prior weekly cut) and the empty-result meaning, 'An empty list means the rosters did not move.'

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?

Four tight sentences, front-loaded with the resource definition before usage, parameters, and edge-case behavior. Nothing is wasted, though the layer restatement is mildly redundant with the schema.

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 zero-required-parameter read tool with no output schema, the description conveys what the ledger contains and how to interpret an empty result, which is the key behavioral gap. It does not sketch the return shape, but the conceptual coverage is otherwise adequate.

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 100%, so the schema already documents all three optional parameters, including layer values and the YYYY-MM-DD format for since. The description largely restates that these are optional and repeats the layer=beyond mapping, adding no new syntax or constraints, so the baseline 3 applies.

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?

States a specific resource and scope: a 'ledger of roster and gathering moves since the prior weekly cut', plus concrete content types (rank moves, entrants/leavers of a top 5). It is distinguishable from siblings like attic_list_gatherings or attic_get_market_report, though it never names them explicitly.

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?

Gives an explicit usage trigger, 'Use this for "what changed", rank moves, names that entered or left a top 5', which tells the agent the question shapes this tool answers. It does not name alternatives or state when not to use it, so it stops short of a 5.

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