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

No annotations are provided, so the description carries the burden of disclosing behavior. It does mention the 20% equity threshold and PMI status, which adds useful context. However, the claim to 'compare multiple down payment scenarios' is ambiguous because the input schema accepts only a single downPct value, potentially misleading an agent about the tool's capabilities.

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?

The description is two sentences, front-loaded with the tool's purpose and key outputs, and contains no redundant or extraneous information. It is well-paced and immediately understandable.

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 simple two-parameter calculator, the description lists the main outputs (down payment amount, loan size, PMI status, gap to 20% equity). However, it does not clarify the multi-scenario behavior, and with no output schema or annotations, the agent lacks a full picture of what the tool returns or how to invoke it correctly for multiple comparisons.

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?

The schema provides zero descriptions for the parameters, so the description must compensate. It explains that price and downPct feed into down payment amount, loan size, and PMI status, and introduces the 20% equity threshold, providing meaningful context. However, it does not detail how multiple scenarios would be passed, and units are implied rather than explicit.

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 clearly identifies the tool as a down payment calculator that calculates down payment amount, loan size, PMI status, and the dollar gap to 20% equity. This distinguishes it from sibling calculators like mortgage_piti_calculator or car_loan_calculator, which focus on different financial aspects.

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?

There is no explicit guidance on when to use this tool versus alternative mortgage-related calculators. The description only states what it does, not when it should be preferred or what prerequisites exist, leaving the agent to infer usage context.

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