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

With no annotations provided, the description must carry the full behavioral burden. It discloses that data is updated daily and costs 2 credits per call, and describes the return content, but omits authentication needs, rate limits beyond credits, and error behavior. This partial disclosure merits a 3.

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 front-loaded with the primary return value and structured logically. The parenthetical list of all 11 sectors is somewhat verbose but informative; overall the four sentences are efficient and earn their place.

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 no output schema and no annotations, the description explains the return values well (breadth score, rotation direction, leaders/laggards, momentum, advance/decline ratios) and adds operational context like daily updates and credit cost. It is nearly complete, missing only minor details like response format or authentication requirements.

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?

There are zero parameters, so the baseline score is 4. The description does not need to add parameter meaning beyond what the empty schema provides.

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 a specific verb ('Returns') and resource ('breadth score and rotation direction for all 11 US stock market sectors'), making the tool's output clear. However, it does not explicitly differentiate from siblings like get_market_regime or get_trading_signals, so it falls short of a 5.

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 guidance on when to use this tool versus alternatives, nor any prerequisites or exclusions. The cost and update frequency are not usage guidelines, just operational facts, similar to the MID calibration example where update_drive received a 2.

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