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

Annotations declare readOnlyHint=true and idempotentHint=true, which cover the safety profile. The description adds context that it returns VIN, year, make, model, and notes that state is required for US plates. However, it doesn't disclose potential failure modes (e.g., unknown plate, rate limits) or response format, but with annotations covering safety, the description adds modest context.

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 description is concise (one sentence plus an example), which is efficient. The purpose is front-loaded, and the example is a useful inclusion. No wasted words, though the example duplicates schema examples.

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?

Given annotations (read-only, idempotent) and 100% schema coverage, the description is adequate but lacks details on potential errors or when to prefer other tools. It covers the what and a basic example, but misses edge cases or limitations.

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 covers all parameters with descriptions (100% coverage). The description doesn't add extra meaning beyond the schema; it explicitly mentions plate and state, and the example illustrates usage. Since schema is complete, 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 clearly states the tool's purpose: 'Decode a license plate → VIN & vehicle' and specifies it returns VIN, year, make, and model for US plates. It distinguishes from siblings like carsxe_history and carsxe_market_value by focusing on plate decoding.

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?

The description implies use for US plates and provides an example call with a CA plate, but it does not explicitly state when to use this versus alternatives (e.g., carsxe_vin_specs for VIN-based lookups). No explicit exclusions or alternative routing are given.

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