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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), so the bar is lower. The description still adds real behavioral value by disclosing the consistency guarantee ('same rule as the movers page') and the empty-result failure mode for short histories, which an agent cannot infer from any structured field.

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 short sentences, front-loaded with the core purpose and followed by the one caveat that matters. The phrase 'the movers page' is slightly opaque as a substitute for a concrete explanation of the ranking rule, costing a point.

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?

There is no output schema, so the description ideally would sketch the return shape (e.g., risers and fallers per board), which it only indirectly conveys via the parameter text. For a simple two-optional-parameter read tool this is adequate but leaves the result structure implicit.

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 the parameter descriptions are unusually informative, explaining that 'limit' is risers and fallers each and that 'category' is a board id with omission meaning all boards. The tool description adds nothing further about the two parameters, 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?

The description names the resource and the metric precisely: 'Week-over-week brand movers', which clearly distinguishes it from siblings like get_brand or get_category_board. The verb is implied rather than stated ('get'), and the reference to 'the movers page' assumes UI context an agent may not have.

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 clause 'A short history returns no movers' is a useful precondition that tells the agent when the tool will yield nothing. However, there is no explicit when-to-use guidance relative to siblings (e.g., get_brand vs. this) and no statement of what history length is sufficient.

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