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

Annotations already establish read-only, non-destructive, closed-world behavior, yet the description still adds substance: the qualifying-rate formula (higher of contract + 2% or 5.25%), the 39/44 GDS/TDS thresholds, the three-state pass/close/fail result, and the exemption logic. It does not discuss rounding, assumptions, or limits on the max-home-price back-solve, so it falls just short of full transparency.

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 sentences, front-loaded with the action and OSFI context, then the results, then the exemption carve-out. The long enumeration is information-dense rather than wasteful, though the mid-sentence output list is slightly harder to scan than separated clauses would be.

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 16-parameter tool with no output schema, the description does the necessary work: it names what comes back (qualifying rate, ratios, verdict, max price, shortfall) and flags the case where the tool returns an exempt result. Minor gaps remain around result units and how the close band is defined, but nothing critical to calling 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 coverage is 100%, so baseline is 3, but the description earns more by explaining how inputs are consumed: which rate becomes the qualifying rate, which ratio thresholds apply, and why renewalIncreasing matters for exemption. That gives an agent meaning beyond the per-field text without duplicating it.

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?

Names a specific verb ('Check') and a precisely scoped resource: the OSFI B-20 stress test for purchase, renewal or refinance. It also enumerates the outputs (qualifying rate, GDS/TDS, pass/close/fail, max home price, shortfall), which separates it from generic siblings like mortgage_qualifier, mortgage_affordability and debt_service_ratio without needing to name 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?

The three supported scenarios are stated explicitly, and the last sentence gives a genuine exclusion rule: straight-switch renewals are exempt unless the amount or amortization increases, which maps directly to the renewalIncreasing flag. It stops short of naming sibling tools to use instead when the case is out of scope (e.g. plain payment or affordability math).

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