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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), but the description adds a substantive behavioral limit: 'No probability is computed: the answer says how large the moves would be, not how likely.' That prevents a plausible misuse of the result. It stops short of describing cost, rate limits, or how the 'least extreme' combination is selected.

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 the core behavior, then usage routing, then parameter notes, then the probability caveat. Every sentence carries information; the parenthetical glosses are slightly redundant with the schema but not wasteful.

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 read-only analytical tool with an output schema, a fully documented input schema, and sibling routing, the description supplies everything an agent needs: what it computes, when to pick it, and the key interpretive limitation.

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 the nested holdings object is thoroughly documented in the schema itself. The description's 'loss is a fraction (0.25 is a quarter); base sets the currency (default USD)' largely restates what the schema already says, so it adds little beyond the baseline.

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 ('starts from a loss... finds the least extreme combination of market moves that would produce it on this portfolio') and explicitly contrasts with the sibling past_crises. An agent can distinguish it from the 21 other tools without opening a schema.

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 the triggering question verbatim ('what would it take to lose that much?') and names the alternative for the opposite question ('for what past crises actually did use past_crises'). When-to-use and when-not-to-use are both explicit.

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