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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds meaningful behavioral context: the shared window constraint, the specific measures computed, and the explicit limitation that it does not recommend which portfolio to hold. 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?

Two compact sentences with no wasted words. The core action and scope are front-loaded, metrics follow, and the key limitation is stated at the end. Every clause earns its 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?

With a rich output schema, detailed parameter schemas, and safety annotations, the description covers the essential behavioral context: scope, metrics, shared window, and non-recommendation boundary. It is complete enough for an agent to select and invoke correctly, though it could optionally mention how the shared window is determined.

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 reinforces the 'up to eight portfolios' constraint already present in the schema and adds the 'shared window' context, but it does not add new meaning about the `base` parameter or the portfolio label/ticker structure beyond what the schema already explains.

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 uses a specific verb ('Measure'), names the resource ('portfolios'), and precisely scopes the action: 'up to eight portfolios over one shared window of price history.' It lists the computed metrics (growth, volatility, worst fall, correlation-like behavior) and distinguishes itself from a recommendation tool with 'does not say which to hold.'

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?

The description gives clear context: this is for comparing multiple portfolios side by side over a shared price window. It implicitly differentiates from the single-portfolio sibling `measure_portfolio` by emphasizing 'up to eight' and 'against the others.' It does not explicitly name alternatives or state when not to use it, but the intended use case is clear.

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