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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description adds genuinely new context the annotations do not: this call costs no credits, which matters next to paid siblings like valuation. It stops short of noting failure behavior for invalid VINs.

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?

Two lines, cost notice front-loaded where an agent will see it before deciding to call, and the return contents summarized compactly. 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?

An output schema exists, so the return-field list is somewhat redundant, but the free-vs-credit distinction is essential context for choosing among siblings. The only real gap is the absence of any routing cue against get_vin.

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 schema's own description already specifies the 17-character format, the excluded letters I/O/Q, and case insensitivity. The description adds nothing about the parameter, so the baseline 3 applies.

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 (returns) and resource (specs for a VIN) with scope ('listed or not'), so the agent knows what it does. However, it never contrasts with the sibling get_vin, leaving the agent to guess why two VIN tools exist.

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?

'listed or not' faintly implies this is the fallback for VINs not in the catalog, which is the only usage signal present. There is no explicit when-to-use, no mention of get_vin as the alternative, and no prerequisite guidance.

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