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

Annotations already cover the read-only/idempotent/no-destruction profile, and the description adds genuinely new context: it requires sign-in or an API key, results are capped by plan, and there is no listing mode. These are behavioral constraints the annotations do not express.

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 dense sentences with the return contents front-loaded, then usage, then the query-anchored constraint and auth note. Every clause carries information; only the 'range they produce' phrasing is slightly vague.

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 compensates by enumerating the returned fields (title, final price, sale month, state, range) and the auth/plan constraints. Only the exact shape of the produced range and per-param defaults are left implicit.

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 60%, so several parameters (q, limit, country, category) rely on their own schema text. The description corroborates 'state' as the sale's state/region and frames q as an item description, but adds little syntax or format detail beyond the schema.

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?

Names a specific resource (individual archived sales behind an item) and enumerates its content (title, final price, sale month and state, range). It implicitly distinguishes itself from get_sold_comps with 'the evidence rather than just the number,' but never names the sibling explicitly.

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 when you want the evidence rather than just the number' gives clear selection context, and 'Query-anchored — describe an item; there is no way to list the archive' rules out a browsing use case. It stops short of explicitly naming get_sold_comps as the alternative when a single number suffices.

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