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

Annotations already mark this read-only, non-destructive and open-world, so the safety bar is low. The description still adds real behavioral context beyond them: how 'restated' model changes are reported separately from the move, that unexplainable aircraft are counted rather than estimated, and the availability gating on stored daily valuations.

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 core purpose is front-loaded and the follow-on sentences each carry distinct information (drivers, restated handling, availability). The first sentence is dense and the 'Aircraft the period cannot be explained for are counted' clause is slightly awkward, but there is little dead weight.

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?

With an output schema present, the description need not explain return values, and it covers the key behavioral caveats (restated, unestimated aircraft, availability gating) an agent needs. What is missing is the sibling comparison for correct tool selection, which matters given the six-plus adjacent portfolio 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?

Schema coverage is 100% and both parameters carry descriptions, so the schema already documents them. The description only restates the window enum/default and does not add format or interpretation detail beyond what the schema provides. Baseline 3 is appropriate.

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 (why a portfolio's value moved) plus the resource (portfolio value) and enumerates the drivers of the move. It implicitly separates itself from the daily-vs-monthly sibling get_portfolio_attribution_by_month, but never names that sibling or otherwise explicitly differentiates itself, 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?

It gives concrete usage conditions: which window values are valid, what the default is, and that 'available is false until a daily valuation has stored explanations.' However, it never says when to choose this tool over get_portfolio_attribution_by_month or other portfolio-value siblings, leaving the primary routing decision to inference.

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