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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered by structured data and the description adds nothing there. It contributes only the use-case framing and a claim about inputs; it says nothing about aggregation semantics, sample size, or shape of results, though the presence of an output schema lightens that burden.

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?

Three short sentences, front-loaded with the identity of the dataset, then the trigger, then an input note. Zero filler, but the final sentence is wasted space because it is inaccurate rather than informative.

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 low-complexity, zero-required-parameter read tool with a documented output schema, the description supplies enough to select and invoke it. The one gap is the incorrect 'takes no input' claim, which leaves the optional `fields` narrowing undocumented in prose.

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 already documents the single optional `fields` parameter (comma-separated top-level keys to keep) at 100% coverage, so the baseline would be 3. However, the description states "Takes no input," which is factually wrong given that a `fields` filter exists, and it never explains what that filter does — this actively misleads the agent about a usable parameter.

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 first sentence names a specific resource and grouping dimension (sales broken out by label length) and scopes it to four named TLDs (.com, .ai, .io, .co), which separates it from the broader sales siblings like ud_get_market_sales. It stops short of explicitly contrasting with those siblings, so it is clear but not fully disambiguating.

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 it when someone asks how the length of a name relates to its sale price" gives a concrete trigger condition an agent can match against a user question. There is no when-not guidance and no named alternative (e.g., use ud_get_market_sales for aggregate price stats), which keeps it out of the top band.

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