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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description adds real beyond-annotation context: the 'after' figures are counterfactual and the window defaults to the longest shared one unless start/end are supplied. It stops short of describing output format, though the output schema covers that.

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-loads the core purpose, then alternatives, then parameter notes, then the scope caveat — a logical order with little wasted text. Slightly dense and clause-heavy in the opening sentence, which keeps it from a 5.

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?

For a nested-object comparison tool, the description covers purpose, alternatives, window behavior, and the counterfactual caveat; annotations carry the safety profile and an output schema exists so return values need no explanation. Nothing an agent needs to call it correctly is missing.

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%, so the baseline is 3. The description goes further by explaining that start/end override the default 'longest shared' window and by restating that current/proposed are the two holding sets, giving the parameter meaning beyond the bare 'Optional window start' text.

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 and resource ('any change to one portfolio, measured before it is made') with the exact output dimensions (structure, risk, worst falls, additions/removals). It also distinguishes itself from siblings by naming check_before_you_buy and sweep_holding with the conditions that select them.

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?

Explicitly routes the agent: for a single new holding use check_before_you_buy, for one holding at every weight use sweep_holding. It also closes a scope question by stating the tool 'never says whether to make the change', so the agent knows the output is diagnostic only.

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