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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuine interpretive behavior beyond that: a sensitivity that cannot be distinguished from zero is reported as such rather than as an actionable number. It stops short of describing output shape or data-window behavior, but with an output schema present that is not a real gap.

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?

Front-loaded with what the tool produces, then usage routing, then parameter notes, then the significance caveat. The nested parenthetical listing the four factors is dense but earns its space; nothing is padded.

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?

Covers purpose, sibling routing, both parameters, and the interpretation caveat, and the return values are carried by the output schema. For a read-only two-parameter analytical tool, an agent has everything it needs to select and call it correctly.

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 both parameters are fully documented there (weights vs amounts, ticker formats, base currency default). The description restates the same facts ('holdings as weights or amounts; base sets the currency... default USD') without adding syntax or constraint detail beyond the schema, 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 verb+resource (decomposing one portfolio's daily moves into four named factor sensitivities) and enumerates exactly what the four patterns are: market, size, value, momentum. It also reports the three outputs (sensitivity, significance vs zero, joint explanatory power), which distinguishes it cleanly from portfolio_structure.

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 trigger ('what style am I really exposed to?') and routes the adjacent question ('how many independent bets there are') to the named sibling portfolio_structure. This is the when/when-not/alternative pattern at full strength.

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