Is this price fair

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

Annotations only cover safety (readOnly/idempotent/openWorld); the description adds the real behavioral substance: confidence thresholds (high 40+, medium 15+), the 'insufficient comparables' verdict when confidence is low, the widening breadcrumb strategy, and that comparisons ignore year/mileage/area/condition and reflect asking prices only.

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 question and the mode split, and nearly every clause earns its place. It is dense with nested parentheticals and confidence cutoffs, which slightly taxes readability but introduces no filler.

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 no output schema, the description carries return-value duty and does so fully (percentile, verdict, vs_median_pct, p25-p75 band, confidence) plus caveats. Both zero-required-parameter modes are explained, so an agent has everything needed to call it correctly.

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 the baseline is 3, but the description adds cross-parameter meaning the schema lacks: token vs price are alternate modes, price means monthly rent for rent categories, and breadcrumb widening derives from the ad. It stops short of documenting every parameter individually, which the schema already does.

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?

Opens with a specific, answerable question ('Is an ad's price ... high or low compared with similar ads?') and names the exact outputs (percentile, verdict, confidence). It distinguishes itself from sibling dv_compare by scoping to market-fairness appraisal rather than ad-to-ad comparison.

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 splits the two invocation modes: with `token` it appraises that ad via its own breadcrumb, without it you must supply `price` plus category/query/filters. It also routes the agent to `filters`/`query` for refinement and to dv_compare for specific-ad comparisons.

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