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

The readOnlyHint annotation already covers the non-mutating nature. The description adds a probabilistic framing ('most likely') and scope to WIG20, but it does not disclose return shape, ranking behavior, or any other non-obvious behavior. There is no contradiction with annotations.

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 description is a single direct sentence with no filler and the key subject is front-loaded. It is appropriately concise and every word contributes to conveying the tool's focus.

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?

Given the large sibling set, the absence of an output schema, and the minimal description, the entry is incomplete for reliable tool selection. It does not explain what output the agent should expect, how the optional parameters affect behavior, or how this differs from related tools.

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 input schema provides full descriptions for both optional parameters, covering date format/default and topN default/max. Schema coverage is 100%, so the baseline of 3 applies; the description itself adds no parameter-level detail.

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 asks what most likely caused the latest WIG20 move, clearly identifying the resource (WIG20) and the general attribution purpose. However, it does not explicitly frame the tool's output as ranked drivers and does not differentiate it from siblings like get_drivers or whats_moving_now.

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?

Usage is only implied: use when one wants an explanation of the latest WIG20 move. There is no explicit guidance on when to prefer this tool over the many market-analysis siblings, no exclusions, and no mention of when not to use it.

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