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

Annotations already cover read-only and idempotent behavior, so the bar is lower. The description adds meaningful behavioral context: it returns both a numeric ratio and a rule-of-thumb signal, includes interpretative thresholds, and explicitly labels itself as not financial advice. This goes beyond what annotations provide.

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 compact and front-loaded: the main computation and scope appear first, followed by the output shape and an important caveat. The phrase 'premium synthesis' is somewhat vague filler, but it does not undermine overall efficiency.

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, read-only computation tool with full schema coverage, the description is complete. It explains the formula, the input scope, the returned values, and the interpretive signal. The absence of an output schema is adequately compensated by describing what the tool returns.

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 schema already documents both parameters well with examples. The description reinforces that 'region' is a US metro or state and contributes formula context, but it does not need to add parameter-level detail beyond what the schema provides.

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 states the specific operation: computing the price-to-rent ratio for a US metro or state via a named formula (ZHVI / (ZORI x 12)). It distinguishes itself from sibling real-estate tools like realestate_home_values and realestate_rents by framing it as a synthesized buy-vs-rent metric, not raw data retrieval.

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 provides clear context for when this tool is appropriate: when a combined buy-vs-rent ratio and signal is needed rather than raw home values or rents. It doesn't explicitly name alternatives or exclusions, but the formula and 'synthesis' wording make the intended use clear relative to the sibling tools.

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