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

Annotations already declare readOnlyHint and closed-world scope, so the safety profile is covered. The description's real contribution is disclosing the exact metrics returned (spot, range, low, deltas), which is substantial behavioral context given there is no output schema. It stops short of noting currency, region, or behavior for unknown/unpriced models.

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?

A single dense sentence that front-loads the primary value (typical used price) and proceeds through the secondary metrics. No filler, though the comma-list style is slightly harder to scan than a short structured clause would be.

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 usefully enumerates the returned fields and the time horizons (7/30-day, 90-day). Gaps remain around currency/region and what happens when a model has no listings, but nothing needed to invoke the tool correctly is missing.

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% and the single `model` parameter already documents accepted forms (id or name with examples). The description only reinforces the single-model scope, adding no format or matching detail beyond the schema; baseline 3 is appropriate.

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 enumerates exactly what is returned (typical used price, fair range, lowest listing, new price, 7/30-day change, 90-day low) for a single model, which makes the resource and scope unambiguous. It doesn't distinguish itself from siblings like check_price or get_price_history, so an agent can't route between them from text alone.

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?

No statement of when to use this versus check_price or get_price_history, and no prerequisites or exclusions. The 'one model' phrasing implies single-item lookup, but that's inference rather than guidance.

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