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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds real context beyond that: 'Faithful pass-through of Redfin's public aggregate-trends resource' tells the agent the data is public, untransformed, and market-level (not per-property), which shapes expectations. No auth or rate-limit detail, so not a 5.

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 metric list is front-loaded in the first sentence, and the routing sentence is short and useful. The re-statement of both parameter descriptions duplicates the schema, which is mild redundancy but not harmful.

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?

An output schema exists, so return values need no explanation, and annotations cover safety. The description supplies metric coverage, region scope, and the sibling alternative. It does not state whether the trend is a single latest snapshot or a time series, which would be the remaining useful detail.

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 both parameters are already fully documented in the schema, and the description text for region_id and region_type merely restates that schema wording. Baseline 3 is correct; no syntax, format, or lookup guidance is added.

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 resource ('Returns Redfin's aggregate market trends for a region') and enumerates the exact metrics returned (median list/sale price, sale-to-list, offers, days on market, inventory, YoY). An agent can distinguish it from redfin_search, redfin_property, and redfin_estimate without opening any schema.

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?

'Use redfin_search to search Redfin listings' names the sibling alternative and the boundary (this tool is for aggregate trends, not listings). It lacks an explicit when-not statement or prerequisite guidance, but the alternative is clearly routed.

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