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 still adds meaningful context that it never reads from chats, files, accounts, documents, or the web and that outputs are ratios only. Nothing contradicts the 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?

Front-loads the calculation, then the disclaimer, then the input-provenance constraint. Sentences are purposeful, though the repeated no-approval/no-recommendation framing is slightly redundant.

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 and annotations covering safety, the description supplies the remaining needed context: scope (Canadian), input provenance, and the guarantee that only ratios are returned. An agent can call this correctly without further information.

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 75% and most parameters carry their own descriptions, so baseline 3 applies. The description only loosely hints at the value basis ('purchase price, an appraised value, or both') and does not explain lesser_of, effectiveDate semantics, or storedLtv, adding little beyond the schema.

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 two named resources (LTV and CLTV) plus the exact inputs it operates on (loan amount, other secured positions, purchase/appraised value). That is clearly distinct from siblings like calculate_debt_service and calculate_qualification.

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 scopes usage to Canadian calculations driven by explicit, non-identifying numbers supplied in the request, and rules out approvals, underwriting, recommendations, and lookups. It does not name a sibling as the alternative path, so it stops short of a 5.

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